I think the key point here is that an API is a specification of functionality, and therefore is an idea (the idea being the idea of program which other code int

I think the key point here is that an API is a specification of functionality, and therefore is an idea (the idea being the idea of program which other code interacts with in a particular way). There is no way to write a runtime environment compatible with Java programs without having the same API (and its possible to develop an identical API only looking at the documentation). While it might involve creative work to come up with an idea, ideas aren't copyrightable[1]. On the other hand, the implementation of an API is clearly an expression of the idea of a particular public interface, so it should be protected by copyright. IANAL though. Edit: As a secondary point, remember that the point of copyright isn't to protect authors, it is "To promote the Progress of Science and useful Arts". [1] https://en.wikipedia.org/wiki/Idea%E2%80%93expression_divide https://en.wikipedia.org/wiki/Idea%E2%80%93expression_divide