[bcg1]

I think we are actually in agreement here... it seems as if you consider "API" to mean the documentation of the function, while I am considering it to be the actual compiled Java bytecode (which is not a description of the function, it actually is the "tangible" function)

If the copyrightable work is the description of the API... then I would argue that simply writing "int cupcake(int x)" is not expressive in a way that can be copyrighted, since it is really the only precise way of describing the bytecode. However any extra information (such as Javadoc comments or other documentation) could definitely be expression.