Legal Harrasment
Q: Unless there is a clear precedent, I'm sure large companies have
enough monetary resources to circumvent US law via forms of legal
harrasment. The question is, is it unambiguously clear that
programming languages are not copyrightable?
A: Names probably can't be copyrighted. I don't think that APIs can be protected if they are necessary for interoperation. The libraries are copyrightable, but that wouldn't protect them from being cloned using "clean room" methods. Most things are not so ambiguous that you can guarantee that a law suit would be immediately dismissed. There is case law supporting the contention that programming languages are not copyrightable but it may be possible to distinguish some given case with past precedent.