I don't think API copyright is recognized, even in the U.S. Logically speaking it shouldn't constitute a copyrightable work, but you never know sometimes. The documentation could be considered copyrightable, though you could just reverse engineer it.

It's kind of the same category as fonts and recipes, which you can figure out by inspection mostly. If you want to protect something like that then a patent might be in order, though let's not get into that mess...