Why are there issues with public domain in Europe, that forces public domain projects to use CC0, 0BSD, Unlicense or other similar licenses?
I.E. why is it that, when someone dedicates a work to the public domain, someone in Europe can still get into trouble for using it? Isn't the copyright holder the only person that can sue? Or is there some other law in Europe?
With respect to my colleague planetmaker, public domain is not a US-specific concept. It dates back to the first copyright law in the world, Britain's 1710 Statute of Anne, where it was referred to as publici juris ("of public right"). French jurists further developed the idea and we see the term "fall into the public domain" entering the discussion in mid-19th Century France, to refer to the fate of a creative work after all the time-limited rights reserved to the creator expire.
The problem to which I think the OP is referring is that of moral rights. Some implementations of copyright law recognise more controlled rights than the economic right - the right to exploit the commercial potential of one's creation. In particular, many jurisdictions recognise the creator's moral rights - the right to be attributed as the creator of the work, and the right to the integrity of one's work (that is, the right not to be attributed as the creator of modifications of one's work of which one does not approve).
The problem is further compounded because in some jurisdictions, primarily civil law ones, the author's moral rights are inalienable. That is, the author cannot lawfully give up those rights, however much (s)he wants to. France and Italy are examples of such jurisdictions.
In those jurisdictions, if an author says "I have no interest in this work, do as you please with it", you cannot know that (s)he intended to waive his/her moral rights. The author might know full well that those rights are inalienable, and intended only that others should have the right to profit from his/her creation. (S)he might well turn out to be very annoyed if an "unsuitable" adaptation appeared, and his/her name was associated with it without even a by-your-leave.
That said, this risk isn't huge. I don't think I've ever heard of it happening in respect of a work where the creator had abandoned his/her economic rights. Secondly, if it does, then it seems to me that changing the name of the project and removing all references to the original author will likely suffice.
But for those seeking clarity, licences like CC0 are specifically intended to implement a simple method of putting a work into the public domain in so far as is legally possible in any given jurisdiction. As Creative Commons note:
many legal systems effectively prohibit any attempt by these owners to surrender rights automatically conferred by law, particularly moral rights, even when the author wishing to do so is well informed and resolute about doing so and contributing their work to the public domain.
CC0 helps solve this problem by giving creators a way to waive all their copyright and related rights in their works to the fullest extent allowed by law
Using a licence like this makes it clear that you, the creator, are relinquishing all legally-relinquishable control of your work, and would like to go the whole way if you were permitted. Anyone who chooses to use your work can then decide for him/herself what sort of jurisdiction (s)he's in, and respect moral rights if that's what the local jurisdiction requires. Anyone using that adaptation can know that the original author intended this to be possible, and is therefore particularly unlikely to start filing suit.
Edit in response to OP's additional questions:
I have seen several people say that certain jurisdictions do not recognize the right to waive copyright and/or moral rights. But who can enforce that?
Nobody has to enforce it. In those jurisdictions, the author simply can't waive those rights, however much (s)he wants to.
Can someone other than the author sue
That will be jurisdictionally-dependent, and is beyond the scope of this site.
can the author act in bad faith claiming that the public domain dedication is legally unenforcable even though the intention is clear?
No bad faith is required. In such jurisdictions the moral rights aspect of the public-domain dedication is indeed invalid, however clearly the intention is expressed.
The utility of CC0 (and similar licences) is to clarify that the author intended to waive even the moral rights wherever possible, and is thus unlikely to sue in those jurisdictions where (s)he retains them. One could argue under the doctrine of promissory estoppel that an undertaking had been given not to enforce those rights, even though they couldn't be waived, and this might well provide a defence if a creator were ever to sue. Failing that, the mitigation measures I outline above aren't exactly painful.
I will give an example specifically for the jurisdiction that I am most familiar with, which is Germany.
Germany doesn't have "copyright". We have "Urheberrecht" (literally translated "Originator's Right" or "Creator's Right", but usually translated as "Author's Right"). In German Author's Right, there is a notion of the work being somehow a "brain child" of the author. There is a connection between the author and their work that goes beyond any form of commercial interest, that is almost metaphysical. (In German literature, this is called the "Band" (roughly "bond") between a creator and his work.)
This is also the reason why it is simply impossible for corporations to be authors and thus hold Author's Rights, whereas it is completely normal for corporations in the US to be copyright holders.
Urheberrecht is split into two distinct subgroups:
The Moral Rights, in particular, are:
These Moral Rights cannot be transferred and cannot be given up. (Remember the "bond" between an author and their works.)
That is the reason why you cannot "put a work in the Public Domain" in Germany.
But there are also limitations on the "Exploitation Rights" (which correspond more closely to e.g. the US idea of copyrights).
There was a landmark case a while ago (I unfortunately don't remember the name, it was a case at the Bundesgerichtshof and it must have been before 2000) that restricted the rights that an author can sign away. Roughly, journals and magazines started to create digital archives with search engines, and sold these archives or access to them. (Seems obvious to us now, but wasn't nearly so in the 1980s.) Journalists typically had contracts with the magazines / journals stating that all exploitation rights for works created in the employ of the magazine belong to the magazine.
The court found that, even though the journalists had signed away "all rights", that actually only meant "rights for usage that commonly existed at the time the contract was signed". Since the lawsuit was about creating archives of old content, the court found that, e.g. for articles written in the 1950s, 60s, 70s, the right to use the articles as part of an electronic database was not included, even though the journalists had explicitly signed away "all rights". The court argued that, since this kind of usage did not exist before, you couldn't have willingly agreed to give up your rights to it.
So, even if you interpret "Public Domain" as "signing away all exploitation rights", that *still doesn't work in Germany", because "all" doesn't actually mean "all", it means "all, as far as we know today".
It's actually very simple:
The term "public domain" is not a legal term, it's strictly US-specific. So it bears no meaning legally outside US. (So in reality US is special here, not "the rest of the world".)
You cannot give up authorship nor copyright. If you want to concede rights for everyone to use your work in perpetuity, use words (a license) which does bear legal meaning - so that they can rely on the words of the license to hold up in court.
So yes, of course you, as author, can write "I put it under public domain". And no-one will be in trouble, if you don't go to court as author. But due to the circumstance that it is not a legally - defined term you can come at any later time and still sue for infringement. That's why people insist on a license to make clear that work can be used under a CC-0 license or similar.
In France authors (including authors of software, even open source ones paid by their employers or clients) have a moral right which cannot be transferred (e.g. to the employer or client).
The CECILL license has been carefully designed to be compatible with French laws.
You might be interested by joining OpenSource.org providing some expertise and hints about many open source licenses.
In France, the APRIL and AFUL non-profit organizations has several legal arguments (usually in French) related to your question. And the French Systematic competitiveness cluster has written a good summary related to legal aspects of open source licenses. The topic is really complex. You could also contact EFF and (in the USA) the FSF (and in French, La Quadrature du Net or FramaSoft).
Notice that the GPL-violations.org website is located in Germany.
Isn't the copyright holder the only person that can sue?
As far as I know, this is false in France. If you are paid for coding, the code is usually (at some point) copyrighted by your employer or client, but you can go to court (e.g. to defend your moral right).
Of course, I am not a lawyer !
PS. Disclaimer: I am employed by CEA, one of the organizations driving that CECILL license (and member of Systematic). I am, as a private individual, member of APRIL and AFUL and FramaSoft.
