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Open-source licensing for frugal science

December 16, 2020

a practical FAQ-style introduction

Table of Contents

What is this article?

This is an introduction to the whys and whats of open-source licensing for hardware projects. This guide is written for you if:

  1. you're working on a project involving hardware, especially frugal science hardware, and you want to share it,
  2. you don't know much about open-source, and
  3. you want a simplified "just the basics" understanding of what questions to ask when making decisions about how to share your work.

Everything here is based on information from various sources linked throughout the article, but especially Github's The Legal Side of Open Source and Kyle E. Mitchell's Open Source: Theory of Operation, which are practical guides written for software programmers. Note that I am not a lawyer, this is not legal advice, the documents which informed this background are not legal advice, and I have not run any of this past any lawyers. If you need to make serious legal decisions, you should talk to a real lawyer and/or do a lot more reading and learning.

If you'd prefer to learn by watching a video rather than reading an article, you can watch the online recording of a lecture/discussion I did on this topic, for the Spring 2022 offering of the Frugal Science course at Stanford. This article expands on the topics discussed in that video and addresses a few additional topics, so after you watch the video I recommend coming back to this post and going directly to any sections which look relevant to you.

What are the key points?

Open-source licensing is a kind of tool you can use to help support your project's strategy for your project's goals. It makes sharing your work easier by giving other people various permissions under the law to use your work if they agree not to sue you for various things which they normally could sue you for. Different licenses give different sets of permissions and place different sets of conditions for activating those permissions. There are two important ways to compare licenses:

  1. What kinds of work they cover: some licenses (such Creative Commons) give permission to people to copy and adapt media and data and documents but do not give any permission related to using, adapting, and sharing software or hardware. Some licenses (such as MIT and GPL) give permissions related to software but not to hardware. And some licenses (such as CERN OHL) give permissions related to hardware but not to software.
  2. What kinds of conditions they place: some licenses (which we call "reciprocal", but you might also see the terms "copyleft" or "share-alike") require that any adaptations of the released work also need to be shared under the same license or a similar license. Other licenses (which we call "permissive") do not have this condition.

Companies with money for lawyers can try to enforce licenses by suing other companies who have violated the licenses. Community projects usually don't have the resources to do that. Instead, they may choose a license to express and implement their goals, and they may try to build social and cultural norms in the community to encourage people to respect the license.

You should choose a license to share your work, so that other people know they're legally protected to use it in certain ways, and so that you're legally protected from certain kinds of lawsuits. If a standard open-source license written by a lawyer does most of what you want, you should use it.

What do licenses do?

Licenses are documents which act as legal tools. They give other people legal permissions to do certain things with our work. Open-source gives us legal tools for releasing and sharing our work, in the context of intellectual property law (copyrights and patents) and contract law (warranties, liability, formation).

In the US, the legal defaults specify that others are not protected from getting sued by us for many things (e.g. copying our work or using our work, at least for media and software) and that we are not protected from getting sued by others for many things (e.g. foreseeable damages resulting from our work). Individuals or businesses typically use lawyers to negotiate private licenses and contracts with other individuals or businesses to override those defaults on a case-by-case basis. They may also release the work to the public under a public license which overrides the legal defaults for everyone; the public license may be used as a substitute or supplement for case-by-case private licensing.

Why should we care?

Most projects will have most or all of the following goals:

  1. Not getting sued
  2. Making an impact
  3. Being able to continue doing the work
  4. Receiving credit for the work

Additionally, many community projects will have the following goals:

  1. Building a community to contribute to the work and carry the project forward
  2. Encouraging others to build on the work
  3. Encouraging others to start their own community projects

Projects involving people who aren't just volunteers will have the following goals, usually because of the overall goal of "being able to continue doing the work":

  1. Making ends meet: paying the bills, paying for food, paying for medical care, etc.
  2. Satisfying people who are giving money to the project, such as customers, clients, or investors

The terms of a project's license will impact how other people interact with a project, what they do with it, and thus what direction the project goes in. Good licenses will give you various legal protections against being sued, which is important if you're giving away your work for free. Some licenses make it very easy for others to do anything they want by completely giving away the work for free, while other licenses are more selective about what people can do with the work. So licenses can have an important effect on how widely a project spreads and what options the project has for sustaining itself.

What do open-source licenses do?

Open-source licenses are public licenses which provide a replacement set of legal defaults which, in certain ways, make it easier for others to modify, share, and use our work. We want to choose public licenses which provide a set of good defaults to help us accomplish our goals of sharing our work in a way that benefits many people.

For someone else to enjoy the permissions granted by the open-source license, they will have to follow a few license requirements (e.g. attributing our work to us) as specified by the terms of the license. If someone can't meet the terms of our license, which typically would happen if our license has terms requiring them to share things they can't/won't share, they would have to negotiate a separate private license, in which case they wouldn't have to comply with the public license.

Open hardware licenses work differently than open-source software licenses. This is because software falls under copyright law, where by default nobody is allowed to copy the software. Copyright law can also cover art, media, documentation, and data, but there are some nuances to that. Hardware design files may fall under copyright law in certain limited ways, but hardware built using the design files generally falls under patent law and not copyright law. This means that if you don't have a patent on your work, the law is going to be less useful to you in enforcing your license.

What options are there?

The biggest differences among open-source licenses are in what kinds of work they cover. Licenses which cover the sharing and use of software don't cover the sharing and use of hardware; and the opposite is also true.

The next biggest differences among open-source licenses are in what default requirements they impose for using/sharing/adapting the licensed work.

Some licenses require that work adapted from the licensed work must be shared under the same license or a similar license. These are typically known as "reciprocal" or "copyleft" terms. Reciprocal licenses have some differences about what situations trigger that requirement for sharing. Examples of well-established standard licenses in this category:

Other licenses have fewer requirements and are called "permissive". Usually they are written in a spirit of "we're giving this away so you can do whatever you want with the fewest barriers, just give us credit and don’t sue us". For example:

Why is it so hard to read these licenses?

Some licenses can be very long. Most licenses are written for lawyers and use very technical legal words. Unfortunately, this usually means that it's harder to understand for normal people. This is still an unsolved problem.

Some licenses have a FAQ section or a human-readable summary to help you understand what they're doing (e.g. the Creative Commons licenses). There are also some very new, somewhat experimental software licenses written in plain English for everyday people (e.g. the Blue Oak Model License), but they're not widely used yet. I'm not aware of similar licenses for hardware. I think we need more everyday-language licenses if we want to have good licensing options for frugal science projects, and we also need licenses which would be easy to translate across a variety of languages and countries.

How are licenses enforced?

Usually enforcement of licenses is done to make license violators start respecting the licenses rather than to collect legal damages for the license violation. In practice, legal enforcement of open-source licenses can be difficult or out-of-reach for community projects. Outside the courts, enforcement can be done by naming license violators to remind them of the risks for their community goodwill and reputation. But for small projects, it may be hard to discover license violations in the first place. So for our projects, the open-source license is useful less as a legal hammer to use against others and more as a strong encouragement of the values and practices we want people to follow if they engage with our work.

Can we just use Creative Commons for everything?

From a legal perspective, this won't do what you think it'll do. But it might be good enough for you, from a practical standpoint where you probably can't afford a lawyer to enforce your license anyways.

Legally speaking, Creative Commons applies to distribution and copying of your design files because those files are covered by copyright law. But it doesn't apply to distribution of hardware people make using your design files. If all you want to do is share your hardware design files and let other people do whatever they want (including not crediting you on hardware they make using your designs) but you still want to give yourself protection against lawsuits and you still want to be credited in any adaptations of your design files, then CC-BY would be a good option. But if you want share-alike conditions in the license, the Creative Commons licenses wouldn't have legal power over hardware built using your design files. If you don't care about the legal side of open hardware licenses, then maybe a Creative Commons license does capture the spirit of what you want for your hardware project, e.g. "I can't actually make you give me credit on any hardware you make using my design file, but I'm still asking you to give me credit".

However, if your project includes software, you should review the reasons Creative Commons recommends against using a CC license on software.

How do we choose a license?

The first thing you'll need to do is look at any third-party works you'll use (e.g. software libraries, or hardware designs) in your work, and look at what licenses they have. The license you choose will need to be compatible with their licenses - so, for example, you cannot use a GPL-licensed software library and release your software under a permissive license like Apache, although you can use an Apache-licensed software library and release your software under a reciprocal license like GPL.

Next, you'll need to prioritize your project's goals and values for the problem your project is trying to solve. Different licenses will make sense for different goals and values and situations. The project's highest-priority goals and values should guide what license you choose. It may be helpful to imagine some scenarios and see how you feel about them (e.g. "if a company wants to use our work, what's okay for them to do without asking us?"), as well as to write out the purpose of your licensing strategy, independent of whichever license(s) you choose.

Then you'll need to look at the available choices to see which ones fit with your priorities. There probably won't be a perfect fit, but hopefully one or two meet most of your top priorities and some of your lower priorities. You might find useful this comparison I did of various hardware and software licenses, where I tabulated all the messy details about what makes each license different; I created this to identify a set of choices of license combinations for the Pufferfish ventilator project to choose between as a replacement for a temporary custom license our project was using.


An easy and accessible resource is Github's Choose a License guide, which recommends licenses by popularity and reputation. If those factors aren't your highest priority for choosing a license, then you'll need to do a bit of reading about options, and you should read and understand any license you're considering. Permissive licenses are the simplest and most common, so you may want to start there to develop a feel for what different licenses do differently. If you want to understand your options for reciprocal licenses, Kyle E. Mitchell's How to Speak Copyleft is a must-read because it provides a framework for comparing different reciprocal licenses, which tend to be longer and more complicated than permissive licenses.


This where you'll need to dive a bit deeper: unfortunately, I haven't found comprehensive resources which I like yet, and open hardware licensing is still a young area. There are fewer license options, which can be good because it means you don't have to evaluate so many options, or it can be bad if no license does what you want.

What about medical devices?

This is a more complicated topic which deserves its own post. What I'll say here is that if you're sharing a design for a medical device, I strongly recommend that you choose a license which includes a warranty disclaimer so that, if something goes wrong, other people or companies don't sue you for their decision to make medical devices using your design. The license should make them take all responsibility themselves as a condition for using your design. You should also be aware that there are other things to be thoughtful about outside of licenses and warranty disclaimers.

How long can we wait before choosing a license?

Choosing a license can feel like a commitment, and you already have so many other important things to do for your project. If any of the following apply, then you should choose a license as soon as possible:

  • Your project uses somebody else's work which was released under a reciprocal license. Then you will need to look at whether you have to release your work under the same license, and whether you want to do that or whether you want to replace that work with something else.
  • You are ready to share your work with other people so that they can use it, share it, adapt it, etc.

Even if these don't apply to you, starting a conversation with your team about licensing is a great way to start a broader conversation about your team's values and goals, and what strategies you want to use for building a community around your project. So I recommend at least starting this conversation as early as you can, even if you don't choose a license quickly.

Can we change our minds about licenses later?

Changing licenses for a project can get complicated quickly, but it really depends on your project, how much progress it has made, what license you were using, what license you want to use, and how your project has gotten contributions from people. Refer to Github's The Legal Side of Open Source for a discussion.

Can we just not use a license?

If your frugal science project starts small and obscure and stays small and obscure, in practice nobody will really care about your lack of a license, because they won't care about your project. Also, in countries with a different attitude to intellectual property law than the US and Europe, or communities where intellectual property isn't a relevant everyday concept, choosing a license might not be practically important if there's already a good culture of sharing work (for example, consider the Jaipur Foot).

But be aware that if you share your work without a warranty disclaimer (which is something all good licenses have), then people may be legally allowed to sue you for many many things, more than necessary. And know that people who take intellectual property seriously (e.g. companies, open-source projects, and people who are very involved in online open-source communities) will avoid unlicensed work, or if they are in open-source communities they may ask you about your license.

Dealing with licenses may feel like a lot of trouble. If it helps, you can make some basic decisions now and do the bare minimum effort now (e.g. adding a license notice, making sure your license is compatible with the licenses of any work you're using from other people, and being careful about contributions to your project from companies) to prevent headaches later. Then you can delay making further decisions until your project has something interesting which you want to share with the world.

Since you probably won't be able to use the legal system to enforce your license, you could choose a license based on how simple and easy it is for other people to understand, and/or how standard it is, and instead focus on developing social norms in a community around your work.

What are noncommercial licenses?

If you're working on a software project, the Prosperity Public License is a clear and concise noncommercial license, which allows free use and sharing of software for noncommercial purposes (note that its definition of "noncommercial" includes developing changes or additions to be shared back to your project under a permissive license). I'm not aware of noncommercial licenses for hardware.

If you've seen Creative Commons licenses, you may have seen its "noncommercial" versions CC-BY-NC and CC-BY-NC-SA, which state that "You may not use the material for commercial purposes", where a "commercial purpose" is defined as one "primarily intended for or directed towards commercial advantage or monetary compensation". The word "primarily" was intentionally included to make the licenses flexible and ambiguous.

For example, if a person with a 3-D printer prints a COVID-19-related face shield for a hospital and accepts money just to cover production costs but not to make a profit, is that primarily intended for monetary compensation, or is it primarily intended for COVID-19 response? There's some legal ambiguity here, and I personally would argue that this scenario is allowed by the license; but as Andre Maia Chagas described to me in an email discussion, the Glia project had problems trying to distribute noncommercial-licensed Prusa face shields to hospitals in Canada for this exact issue. That project created a new design as a workaround, which took precious time. So it's important to think about what your priorities are for licensing, and also think about how ambiguous license text (whether intentional or unintentional) may help or hinder your goals. If you use a license which is more ambiguous than you want, I recommend that you add comments giving people clarification about your intentions and how you want to enforce licenses. For example, the Prusa webpage now says:

We share these files under noncommercial licence. It would be great if you donated these shields to those in need for free. If you need to cover your production costs, we are ok with you selling the shields for production cost. However, we do not want to see these shields on eBay for $50.

Actually, no matter which license you choose, I recommend writing at least a few sentences about why you chose the license and how you understand it. That'll reduce ambiguity and confusion for other people, and it'll help them understand the spirit and values of your project. However, if your project is successful, there will be many licensing situatons and questions you can't anticipate, so you may want to invite people who have questions about the license to contact you. This means that if you want to use a Creative Commons noncommercial license, you should prepare to manage the confusion you may cause if your project succeeds.

Are noncommercial licenses open-source?

Many (or most?) people in the open-source software world have decided that open-source is fundamentally incompatible with noncommercial licenses, and that open source is incompatible with licenses which forbid unethical uses of software; this is loudly policed by the Open Source Initiative (OSI). Their definition of "open source" is also the basis for the Open Source Hardware Association's definition of open-source hardware. There are people in online communities for open hardware who argue that the OSI "owns the trademark 'Open Source'" and thus can sue you if you describe a noncommercially-licensed project as "open-source". But they are just plain wrong, as even the OSI itself says that it cannot trademark the term.

Noncommercial software licenses don't call themselves open-source, but rather "noncommercial" or "source-available" (e.g. PolyForm). If you use a noncommercial license for your work and call it open-source and it gets publicity, random strangers on the internet will feel the urge to strongly criticize your project for not obeying the OSI's definition of "open source"; it's up to you whether they're worth listening to. But you might also get valuable constructive criticism about whether the potential benefits of noncommercial licenses outweigh the potential risks for your project; don't let this feedback get lost between the noise about "open source" definitions.

If you're doing a frugal science project and your values around commercial uses are different from what the OSI demands for open-source licenses, you have several options. Here are three:

  1. You can choose a license which goes against the OSI/OSHWA definition of "open-source", call your project "open-source", and ignore the OSI/OSHWA.
  2. You can choose that license and avoid using the phrase "open source", perhaps using the phrase "frugal science" to help develop it as a community with a different set of values and ethics than "open source".
  3. You can choose a license which follows OSI/OSHWA's definitions, and find other ways to express and enforce your project's values.

All three options can be valid. It's up to you. Ultimately, what matters more is making a positive impact with your project; and the phrases "frugal science" or "open source" can only get practical meaning through how the communities of people who do "frugal science" or "open source" projects define the terms for themselves, not though top-down rules declared by me or you or an industry association trying to build or preserve "open-source" as a commercial brand.

Can we write our own license?

Licenses are legal documents, which means they need to be clear to other people and they need to do the things you want them to do. If a standard license will meet your needs, you should probably use it instead of trying to write your own custom license.

If no licenses meet your needs, you may want to write a new license in a way that it can become a standardized license, since there are probably also other projects facing the same gap. You should have a good line-by-line or even word-by-word understanding of existing licenses. And you should have some understanding of why and how lawyers wrote existing licenses the way they did. If you have experience with open-source software and want to write a hardware license, you should also make sure you understand how legal considerations for sharing hardware are different from those for sharing software. As some starting points on all these things, refer to:

I'd also suggest that your license should be written in plain English so that it's clear and easy for other people to understand without having to rely on a lawyer. Otherwise, you might end up just adding noise into the licensing landscape which makes it harder for people to understand how they can share and adapt frugal science projects. Because there aren't enough tools to help you write a good license on your own, you should get review from a lawyer if you write a license or other legal document.

What about (question not listed here)?

Please ask me this question in the comments box below, or by reaching out to me on Mastodon (details below)! If I can write a general answer, I'll add it to this post. But remember that I'm not a lawyer.

If I made a mistake, I'd really appreciate your constructive criticism so that I can improve this post. If I simplified a concept or issue too much, please leave a comment explaining it, so that other people can learn!

Note that posting a comment below requires you to register or log in on a Github account, because this blog's comments are stored there. If you don't already have a Github account, I recommend getting one because it's the largest platform for sharing and working together on open-source projects (especially software and electronics, but also some other kinds of hardware).


Thanks to the Fall 2020 Frugal Science class for a great discussion which helped me think about what to include in this post! Thanks also to Andre Maia Chagas for valuable information about the problems which the Glia project encountered with noncommercial licensing.

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