A large minority of open-source projects come with a CLA, or Contributor License Agreement, and require you to sign one before they’ll merge your patch. These agreements typically ask you to go above and beyond the rights you afford the project by contributing under the license the software is distributed with. And you should never sign one.
Free and open source software licenses grant explicit freedoms to three groups: the maintainers, the users, and the contributors. An important freedom is the freedom to make changes to the software and to distribute these changes to the public. The natural place to do so is by contributing to the upstream project, something a project should be thankful for. A CLA replaces this gratitude with an attempt to weaken these freedoms in a manner which may stand up to the letter of the license, but is far from the spirit.
A CLA is a kick in the groin to a contributor’s good-faith contribution to the project. Many people, myself included, contribute to open source projects under the assumption that my contributions will help serve a project which continues to be open source in perpetuity, and a CLA provides a means for the project maintainers to circumvent that. What the CLA is actually used for is to give the project maintainers the ability to relicense your work under a more restrictive software license, up to and including making it entirely closed source.
We’ve seen this happen before. Consider the Redis Labs debacle, where they adopted the nonfree1 Anti-Commons Clause2, and used their CLA to pull along any external contributions for the ride. As thanks for the generous time invested by their community into their software, they yank it out from underneath it and repurpose it to make money with an obscenely nonfree product. Open source is a commitment to your community. Once you make it, you cannot take it back. You don’t get the benefits associated with being an open source project if you have an exit hatch. You may argue that it’s your right to do what you want with your project, but making it open source is explicitly waiving that right.
So to you, the contributor: if you are contributing to open source and you want it to stay that way, you should not sign a CLA. When you send a patch to a project, you are affording them the same rights they afforded you. The relationship is one of equals. This is a healthy balance. When you sign a CLA, you give them unequal power over you. If you’re scratching an itch and just want to submit the patch in good faith, it’s easy enough to fork the project and put up your changes in a separate place. This is a right afforded to you by every open source license, and it’s easy to do. Anyone who wants to use your work can apply your patches on top of the upstream software. Don’t sign away your rights!
Additional reading: GPL as the Best Licence – Governance and Philosophy
Some responses to the discussion around this article:
What about the Apache Foundation CLA? This CLA is one of the better ones, because it doesn’t transfer copyright over your work to the Apache Foundation. I have no beef with clauses 1 and 3-8. However, term 2 is too broad and I would not sign this CLA.
What about the Linux kernel developer certificate of origin? I applaud the Linux kernel’s approach here. It covers their bases while still strongly protecting the rights of the patch owner. It’s a short statement with little legalese and little fanfare to agreeing to it (just add “Signed-off By” to your commit message). I approve.
Update April 2021: I wrote a follow-up article about the Developer Certificate of Origin in particular: The Developer Certificate of Origin is a great alternative to a CLA
Free as in freedom ↩︎
Call me petty, but I can’t in good faith call it the “Commons Clause” when its purpose is to remove software from the commons. ↩︎