You can't copyright a softwarw API in the US because they are considered purely functional (in the mechanical sense). Take flathead screwdrivers as an example.

You can't copyright the dimensions of the blade head, since they're just the dimensions of the screw slot, and the only thing the copyright does is harm interoperability between screws and screwdrivers. You can copyright some other aspects of the screwdriver design, and if screwdrivers were a new thing, you could patent the idea of a screwdriver.

This is why the Java case hinged on a former sun employee literally cutting and pasting method implementations he wrote at Sun into Android's implementation while he worked at google. /double-face-palm