The other clue to the importance of copyright came by accident as I was looking at the difference between the emacs editor and the XEmacs editor. Emacs was an open software project that forked in the early 1990's before the terms Free Software and Open Source had even been invented. One of the criticisms that Stallman, speaking for the emacs project levels against the XEmacs project is that they have been sloppy about the ownership of the code and not always got the "legal papers" that assign ownership of the contribution to the project. On this web page about XEmacs versus emacs, Stallman says:
"XEmacs is GNU software because it's a modified version of a GNU program. And it is GNU software because the FSF is the copyright holder for most of it, and therefore the legal responsibility for protecting its free status falls on us whether we want it or not. This is why the term "GNU XEmacs" is legitimate.Note that GNU is the FSF "brand" for its software. The legal papers that Stallman references assign ownership and copyright of a code contribution to the FSF. Because the FSF owns the code it can enforce its right as owner on anyone who breaks its license. Also it can change the terms of the license, and license the code to another party under any other license that it sees fit. The FSF has changed the license terms of the code that it owns. As new versions of the GNU Public License (GPL) have emerged the FSF have upgraded the license to the latest version.
"But in another sense it is not GNU software, because we can't use XEmacs in the GNU system: using it would mean paying a price in terms of our ability to enforce the GPL. Some of the people who have worked on XEmacs have not provided, and have not asked other contributors to provide, the legal papers to help us enforce the GPL. I have managed to get legal papers for some parts myself, but most of the XEmacs developers have not helped me get them."
Copyright and Open Source is a study in contradictions. On the one hand, Richard Stallman has "campaigning against both software patents and dangerous extension of copyright laws". On the other hand, he uses ownership of copyright to push his agenda through the GNU Public License which has a viral component so that the source code of any software that is linked with GNU licensed software must be published as open source software. I will write more about this issue.
A good Open Source project needs to make sure that everyone who contributes code to the project signs a document that assigns copyright of their contribution to the project. Unless care is taken to make all the code belong to a single entity, each person who has contributed to the code owns their contribution. If the project wants to be able to do anything with the code other than passively allow its distribution under its existing license, the code must be owned by a single entity. As Stallman says, the project may not be able to defend its own rights unless the code has clear ownership.