I hear people raise this concern a lot, but I think it is without foundation. If something is in the public domain in the U.S. then anyone can use it for any purpose, including releasing it under whatever license they want. Of course, any constraints imposed by that license will be unenforceable since any user of the software can claim to be using it under the terms of some other license or, of course, as part of the public domain. But if you think you need it licensed, you can have it licensed.
Anybody under U.S. jurisdiction can follow U.S. law.
However if me and my company and everything is in Europe and I use/redistribute the code in Europe I must follow applicable European law. If that doesn't accept that form of public domain the author (rights owner) could sue me and it were upon the judge, who sensible they are. (This is mostly theoretical - if the author decides to put it in public domain per U.S. law they most likely don't want to restrict to U.S.)
> If that doesn't accept that form of public domain the author (rights owner) could sue me and it were upon the judge, who sensible they are. (This is mostly theoretical - if the author decides to put it in public domain per U.S. law they most likely don't want to restrict to U.S.)
Generally speaking, the risk is less the author themselves (though they could always do an about-face for whatever reason, it's hardly unprecedented[0]) and more eventual heirs of them who could always decide to cash in.
That was a completely different situation. In that case, the material was still under copyright in Germany. In this case, the material has been placed in the PD by the original author and so no one in the world can possibly have any legal claim on it.
But if this really concerns you, I would be happy to provide you -- or anyone else -- with a licensed copy of any of DJB's code for a modest processing fee.
> In that case, the material was still under copyright in Germany.
Which is exactly the case of djb's work here.
> In this case, the material has been placed in the PD by the original author and so no one in the world can possibly have any legal claim on it.
Wrong. djb and any possible heir of his does, because you can't place things in the public domain in mainland europe.
> But if this really concerns you, I would be happy to provide you -- or anyone else -- with a licensed copy of any of DJB's code for a modest processing fee.
Unless djb specifically gave you license to do so, your "licensed copy" is worth exactly as much as the original public domain dedication is. As far as european law is concerned, you have no rights to the work, and thus certainly don't have the rights to relicense it.
That is true, but there currently is no precedent for that. Until someone becomes the "sacrificial lamb" by 1. taking the risk and 2. being sued for it, anyone intending to build a business is understandably wary and unlikely to touch public-domain-dedicated assets.
> I hear people raise this concern a lot, but I think it is without foundation.
Well, I've come across companies that have policies against using unlicensed or public domain code.
This sadly makes whether it's a founded concern irrelevant, as the licensing choice suddenly prevents me from using the code in any shape or form if I work there.
> If something is in the public domain in the U.S. then anyone can use it for any purpose, including releasing it under whatever license they want
In the US. Public domain dedications have no legal standing in most of mainland Europe's IP regimes. A public domain dedication is the equivalent of no license at all.
And because a public domain dedication has no legal standing, a third-party slapping a license on the code does not make it legally licensed as far as european IP courts are concerned, they don't have that right, their "license" is worth as much as you deciding to license Windows under GPLv3.
> But if you think you need it licensed, you can have it licensed.
Unless djb offers to provide a fallback license (which incidentally is exactly what CC0 does and why it's legally sensible and valid[0]), then no, you can't "have it licensed".
I am no expert in German copyright law! But your own source says:
"It is worth noting that the result would stay the same if CC0 would not even contain such an explicit fallback rule. According to the prevailing opinion of the legal scholars, public domain licenses (which cannot be interpreted as a waiver of rights under the German copyright, see above) are reinterpreted as unconditional, unlimited, non-exclusive (i.e. public) licenses."
which appears to contradict your statement that public domain dedications are treated as no license at all.
Making it legally dodgy to dangerous in mainland europe, either way certainly not reliably licensed.