Even mere usage could be risky - If I code an application that utilizes most/all of a copyrighted API's objects and methods, then my program may include a reflection or copy of the API I'm using.
Making an API freely available to use by application programmers is an invitation to copy it in a sense. That's part of how its used. Its not much of a leap to say that implies that APIs are a special class of code covered entirely by fair-use if authors do not restrict who can code for them.
In any case... Does not every BIOS depend on APIs? How did we even get the PC compatible revolution in the first place?!