Recently, I wanted a certain functionality that can be difficult to implement due to many special cases and subtle details in technical specifications. So I did a websearch and quickly found existing implementations. One of them said in the header:
I place this code in the public domain (CC0)
Fine. But further, the header said
This code is nearly the same as in [some other open source library]
When looking at the "other library", I saw that it was published under the 3-clause-BSD license.
This led me to the question:
Who is responsible for code being in the public domain?
Note that the question is not about who is "responsible for the code". It is about who is responsible for the fact that the code is available under a certain license. Particularly, I could now copy the code that was said to be in the public domain, without any attribution - and ignore the fact that it might have been copied from a BSD-licensed software without proper attribution.
Of course, one could trivially say: The first person who omitted the BSD header, and stated that the code is in the "public domain" is responsible here. Others, who have copied this "public domain" code cannot be held responsible for this, because they had to rely on the statements of the other authors.
But I wonder how this should work in practice. Someone could copy arbitrary code, remove the license information and declare it as public domain. Others could then use the code without attribution - or worse, may even suggest that they wrote it, and publish it under a more restrictive license, with their name in the copyright statement.
Once such a Pandora Box of public domain is opened, it is basically impossible to figure out who was the culprit. And eventually, this would lead to the question of whether there is any reasonable way to withdraw code that was once placed into the public domain - be it erroneously or intentionally by others.
I slightly reworded the statements from the header. I do not want to accuse anybody in particular, and I do not even want to suggest that any particular author might have done something wrong. I just wanted to set the stage for my question.
I know that one has to be careful with the wording here, and that things like "copyright" and "license" are only remotely related. To my understanding, the border between them is blurred in the public domain / CC0 case, but I am not a lawyer.