Are there any gotchas in contributing public domain code to an open source project? My understanding is that the existence of a copyright gives a project the right to enforce its license. And public domain code is, by definition, non-copyrighted.
What I'm specifically curious about: If an employee of the US government writes source code while on official duty and the federal agency releases it, that code is by law in the public domain. So, in particular, I'm wondering if there would be any issues if a federal agency/employee wants to contribute to an open source project.