What I meant is that the copyright owner is not bound by the terms of a GPL license he grants to others. Similarly, a licensee who receives software from the copyright owner under a GPL license cannot compel the copyright owner to do anything.
An author that licenses the software under GPL, but does not release the source code in that format cannot legally incorporate outsider contributions into his GPL'd work as he would be in a position of infringing the derivative work author's right.
> a licensee who receives ... GPL license cannot compel the copyright owner to do anything.
Unless licensee in question has also contributed to a published revision of original licensor's code. And for that to work (remember the wording "preferred form for modification"), you need a form suitable for modification by a skilled stranger with little prior exposure to said work. You would otherwise get different preferred forms of modification of each contributor, which is unworkable.
> you need a form suitable for modification by a skilled stranger with little prior exposure to said work
That’s a nice idea, but it’s not a condition of the GPL. GPL v2 and v3 both only state, “The ‘source code’ for a work means the preferred form of the work for making modifications to it.” That definition exists because without it a licensee might try to argue that distribution of modified and then obfuscated code satisfies the source code offer condition.
Regarding a project licensed to others under the GPL, if the project owner accepts contributions under the GPL, then he becomes a licensee of the contributions. So, as you pointed out, he would need to meet the “preferred form” clause and other terms, at least as regards to the contributed portions. As you might expect, for a substantial project with many contributors, this could become very complicated. Therefore, many projects require contributions be made under a more liberal license (or even a copyright assignment) that allows the contribution to be sub-licensed to others without conditions.
> Therefore, many projects require contributions be made under a more liberal license (or even a copyright assignment) that allows the contribution to be sub-licensed to others without conditions.
Most, but not all of European jurisdictions, have a legal stipulation that all copyright assignments are either void or revocable even if the assigner says otherwise, except for work-for-hire. You therefore cannot release yourself from preferred form even if you required a copyright assignment, otherwise you will get stuck in the case any further published modifications to your work, not only for the contributions, but any part those modifications that interact so much so that they are inseparable, even by the original licensor, may become illegal overnight. As GPL does not state "the form deemed preferred for modifications by the licensor(s)", but " preferred form ... for modifications", you need to apply that objective definition I stated above. It would be nice if they explicitly stated that way though, relieving a lot of load from judges in resolving a possible dispute on which forms are preferrable for modification and which are not.
It may help to think about who can sue whom. Generally only a copyright owner can sue an infringer. A license operates as a defense against a claim of infringement. If a licensee fails to meet a condition, then the license is invalid.
So, in the case of the project owner who (1) starts out owning all of the rights to the project, (2) incorporates code licensed from a contributor and, (3) distributes the combination, the only person who could possibly sue the project owner for copyright infringement is the contributor. The claim would only pertain to the contributor's code, because that is the only part he owns the copyright to. The project owner/defendant would raise the license as a defense and the key question would shift to whether the owner/defendant violated any of the conditions of the license.
Where the license is the GPL, one of the conditions is partially affected by the "preferred form" definition of source code. The court would look at what the owner/defendant did and whether he met that condition. Importantly, the condition and "preferred form" definition would only be considered in relation to the plaintiff's code; the owner/defendant's code wouldn't be relevant.
Regarding the contributor's code being "inseparable", that will not be the case for one very simple reason: If the contributor sues the project owner, then he must identify which portion of the code he is suing about. If he can't do that or can't show ownership of it, then he will lose.
> license operates as a defense against a claim of infringement
It works like that in fully assignable IP jurisdictions (like USA), but it works like a contract of adhesion in the author's compulsory rights jurisdictions (like Germany and Czechia).
What I meant by inseparable contribution was a significant contribution, when eliminated, that would make entire work not resemble the current state of the work; i.e. the line that tells derivative work versus near-equal co-authorship apart (which are treated similarly in fully assignable IP jurisdictions, yet have entirely different regimes in the compulsory rights jurisdictions). Not the entirety of the work indeed.
> the condition and "preferred form" definition would only be considered in relation to the plaintiff's code; the owner/defendant's code wouldn't be relevant.
It would, in a compulsory rights jurisdiction, because all copyright assignments are either void or revocable at will in such jurisdictions.
> It would, in a compulsory rights jurisdiction, because all copyright assignments are either void or revocable at will in such jurisdictions.
I didn't believe this, so I looked at a study of EU copyright law[0]. Rights of authors are split into moral rights and economic rights. Economic rights are transferable as property. Moral rights, however, inure to the author and are inalienable. In some countries, the moral rights include the right to withdraw the work from circulation. This right to withdraw is probably what you are referring to when you say that copyright assignments are void or revocable.
The right to withdraw a work from circulation, however, does not come for free. In Spain it is only, "after indemnification of the holders of exploitation rights for damages and prejudice."[1] In Estonia, "The rights ... shall be exercised at the expense of the author and the author is required to compensate for damage caused to the person who used the work."[2] In France, "... he may only exercise that right on the condition that he indemnify the assignee beforehand for any prejudice the reconsideration or withdrawal may cause him."[3] In Romania, the right is "subject to indemnification of any holder of exploitation rights who might be prejudiced by the exercise of the said withdrawal right."[4]
In all of the examples I could find, the withdrawal right essentially extinguishes an assignment of the economic rights. So, in a sense you are correct that an assignment is revocable. Practically, however, the author who exercises that right would be liable for damages to the assignee, which could be significant, and the author would not be able to exercise the right if he could not pay for the economic harm.
Anyway, this has been interesting and I learned something about European copyright regimes. Thanks.
