I read the following in ØMQ - The Guide (in Chapter 6, in the section Licensing and Ownership):

All patches are owned by their authors. There SHALL NOT be any copyright assignment process.

Here we come to the key reason people trust their investments in ZeroMQ: it's logistically impossible to buy the copyrights to create a closed source competitor to ZeroMQ. iMatix can't do this either. And the more people that send patches, the harder it becomes. ZeroMQ isn't just free and open today—this specific rule means it will remain so forever. Note that it's not the case in all GPL projects, many of which still ask for copyright transfer back to the maintainers.

I don't understand the last sentence: how can a GPL project ask for copyright transfer back to the maintainers?

Can you give any example[s] of [a] GPL project[s] which do[es] that?

What is a contributor's incentive to make such a copyright transfer to "the maintainers"?

Is this topic (a requirement for copyright assignment) inevitably caused by the maintainers wanting to dual-license the software?

  • Sorry for the downvote; as a newcomer I don't know what's wrong with this question, or why it's unsuitable for this site.
    – ChrisW
    Jul 30, 2017 at 15:43
  • 3
    Don't stress about one downvote; I don't really see why this was downvoted. The first question (what projects do this?) seems like a list question, but the following questions (what reasons do projects give for doing this? why do contributors go along with it?) make it clear it is not a list question. The only other reason I could guess is that this is generally well understood (e.g., the very first GPL project ever, GNU, does exactly this) but obviously you didn't know, otherwise you wouldn't be asking.
    – apsillers
    Jul 30, 2017 at 23:59
  • @apsillers Thank you, yes I had no idea that FSF/GNU does that; and I wouldn't have guessed the reason for it (i.e. that their being copyright holder might help them enforce the GPL). I did ask for a "list", as an example: because I better understand (including why and how) any general rule ("many projects ask for copyright transfer"), if I consider some specific example[s] of it ("for example GNU"). The first reference (CLA) in unor's answer has a good list of examples.
    – ChrisW
    Aug 2, 2017 at 7:09

1 Answer 1


Many projects do this, typically with the help of a CLA (Contributor License Agreement).

Possible reasons for doing this (there might be more):

  • The project owner can change the license without having to ask every contributor for permission. This includes multi-licensing. And it would even be possible to make it proprietary.
  • The project owner can legally enforce the license without having to coordinate with, and involve, all affected contributors.

See for example FSF’s reasoning: Why the FSF gets copyright assignments from contributors

There are many different forms of CLAs. You don’t necessarily have to assign/lose your copyright, and you could exclude certain things (e.g., to prevent that the software becomes proprietary).

See for example FSFE’s Fiduciary Licence Agreement, Canonical’s Project Harmony, and contributoragreements.org.

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