I have read that a simple way to manage contributions was to add "and contributors" to the copyright byline:

Foo project
Copyright 2017 J. Hacker and contributors
Shared under the Libre License version 4 or later

The suggestion was that this meant that any changes made by contributors were implicitly shared under the same license. I have forgotten where I originally read this, but here's a real-world example of someone doing this:

Clarify copyright: "... and contributors". Contributors don't have to assign me the copyright to their contributions; they only have to agree to release their contributions under the same license as the rest of the clang-ctags source code. https://github.com/drothlis/clang-ctags/commit/dbba978ced602d63f425d7c30635db3c5357cc51

Is this true and are there any other implications? (I'm not looking for legal advice, but I am looking for a reliable citation.)


TL;DR: A copyright notice is just the list of the copyright owners. It does not give magic licensing powers. The “… and contributors” is a truism: each contributor keeps their copyright unless they sign it away. This is the same as the absence of any copyright notice.

A copyright notice is not required, but is strongly encouraged. If you have a copyright notice, it should list the correct copyright owners. If a project was started by a single author who later incorporated contributions by other authors, the primary author does not own sole copyright. For projects with lots of small contributions by many people, it would be unfeasible to list all actual authors in the copyright notice. Instead, it is common to list the group of authors as the copyright owner(s), or to explicitly list the primary authors and note that additional authors exist:

Copyright <year> The <project> authors

Copyright <year> <primary authors> and contributors

The complete list of authors could perhaps be in an AUTHORS or CREDITS file, or implicitly in the version control history. But as far as I know, keeping a list of copyright owners is not required, it's just a very good idea to ensure traceability.

If the copyright notice would only list the primary authors, this would indicate they own the complete copyright for the project. In the example you cite, the copyright notice was amended to clarify that this is not the case: every contributor keeps their copyright. That is the default. If copyright were to be transferred, this would require an explicit contract (copyright assignment, usually as part of a contributor license agreement).

Note that some jurisdictions separate copyright from moral rights. Then, copyright only covers economic aspects: the copyright owner may issue licenses. Moral rights cannot be waived in some jurisdictions, and e.g. cover the right to attribution. I.e. even if I sign away my copyright to a contribution by accepting a CLA, I may have a right to be credited as a contributor. The copyright notice is not the place for such a credit.

A specific formulation of the copyright notice does not affect how contributions are licensed. Instead, this would be covered in a contributor license agreement or in the license itself. Notably, the Apache License 2 contains a CLA, and copyleft licenses such as the GPL family limit how derivative works (and therefore contributions) may be licensed. Also, the GitHub terms of service contain a default CLA, but that only codifies the expectation that contributors issue an implicit license when they explicitly submit contributions to a project.

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  • this is very helpful, especially the note that Apache 2.0 and GPL-family licenses basically don't need an extra CLA – lofidevops May 25 '17 at 12:50
  • @d3vid for the GPL licenses a CLA is still good to have. E.g. a contributor to an LGPL project might want to only provide their changes under the AGPL which is not compatible. Additionally, a CLA could ask contributors to license their changes under the GPLvX and any later version, which makes GPL version upgrades possible. – amon May 25 '17 at 12:56
  • thanks again -- followed up with opensource.stackexchange.com/questions/5512 and opensource.stackexchange.com/questions/5513 – lofidevops May 25 '17 at 13:24
  • Very interesting info on the default CLA of GitHub TOS. – Zimm i48 May 25 '17 at 21:24

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