[throwawaykf05]

Actually, formats and languages are not, but the generated machine code is copyright protected as a "derivative work". This is how binaries enjoy copyright protection, because they are "derived" from copyright-protected human-produced code. I think that's a bit crazy that a potentially useful product by itself has no intrinsic protection.

As for method signatures, at a human readable level, they are as protected as any other code. Note that copyright protects expression rather than what the code does. So File.open(fname) and open(fname, 'r') and new File(fname) are all different expressions of the concept of "open a file with a given name)". The concept is not covered, but the specific expression is. Of course, a single method is not sufficient, but this case involves a collection of hundreds of such signatures.

[Zigurd]

I agree about generated machine code. I was referring to an instruction set architecture, that is, the format of the machine code, not the specific sequence of code generated from translating a higher-level language.

I can't agree about method signatures, though. They are like a language, a format, a protocol, none of which are protectable.