CC0 (like BSD/MIT) is basically a quit claim deed.
The US has unilateral copyright assignment though. I always wondered why you could not just assign the copyright to the federal government. Work-for-hire by feds is public domain.
> I always wondered why you could not just assign the copyright to the federal government
Assigning work to the US federal government does not put it in the public domain. Work created by a US federal government employee, in the course of their official duties, automatically enters into the public domain in the United States (but not necessarily internationally.) However, if someone else creates a copyrighted work, and then assigns the copyright to the US federal government, as far as copyright law goes, the US federal government has the same ability to limit access to it (or charge for access) as any private copyright holder does.
It's probably more accurate to say that, in contrast to everyone else in the country, most works created by the US federal government don't get copyrighted upon their creation (in the eyes of the US federal government). That effectively means they're what people describe as in the public domain in the US. But other countries may not recognize the right of the US government to create uncopyrighted works.
> But other countries may not recognize the right of the US government to create uncopyrighted works.
I think that's not the right way of wording it. [0] says:
> 3.1.7 Does the Government have copyright protection in U.S. Government works in other countries?
> Yes, the copyright exclusion for works of the U.S. Government is not intended to have any impact on protection of these works abroad (S. REP. NO. 473, 94th Cong., 2d Sess. 56 (1976)). Therefore, the U.S. Government may obtain protection in other countries depending on the treatment of government works by the national copyright law of the particular country. Copyright is sometimes asserted by U.S. Government agencies outside the United States.
It might be more accurate to say that US law limits the rights of the US federal government to own copyright in its works, but that US law was only intended to apply domestically within the US, not overseas. However, whether it effectively does apply overseas, is not ultimately up to the US, it is up to overseas legal systems – if an overseas legal system wants to make that US law effectively applicable in their country too, that might not be what the US wants, but there is nothing the US can do to stop them, and the US is unlikely to even complain much about it, just because this is not a particularly important issue as far as international relations goes.
I'm not aware of any country (other than the US) whose copyright laws explicitly mention US federal government works. Instead, I think the situation is simply due to this:
a) The majority of countries, their copyright laws just say that any work becomes copyright automatically upon creation, even works created overseas, and they have either no exceptions to that rule, or else no exceptions relevant to this case
b) A minority of countries, have a rule saying that their domestic law will not grant foreign works greater copyright protection than they have in their country of origin. Under such a rule, a US federal government work in the public domain ab initio in the US will also be in the public domain in that country ab initio. (You could interpret this as "the rule of the shorter term" being applied to the case when the term is zero.)
Neither rule was adopted with US federal government works in mind – such works have rather limited economic significance, and as such have never been a major consideration for overseas legislators. It is just how copyright laws, which were adopted for other reasons, happen perchance to apply in this case. Most international copyright treaties permit both approaches, leaving the choice up to each nation's legislators and court system to decide upon.
I don't know if that would work; transferring a copyright to the US government is actually one of the only ways the government gets to own a copyright.
The US has unilateral copyright assignment though. I always wondered why you could not just assign the copyright to the federal government. Work-for-hire by feds is public domain.