> APIs on the other hand, are mainly for humans to communicate with each other when building systems that interoperate.
I guess maybe that'd be the argument. To me, it seems pretty clear that API's are for "computer systems interoperating with each other". That's what an API is, an interface for one piece of software to interoperate with another. Seems to me and many others anyway. "Interface" kind of means "interoperation", an interface is the where and how of one component interoperating with another. I'm a bit surprised that any programmer would disagree actually, but I've been surprised before.
The scary thing is that non-technical judges will have to understand what an API is and what it's for here.
I do agree that software code does some weird things to copyright and starts to make the whole thing odd, and agree with you about "method of operation" thing -- the trick about code, different from former "creative expression fixed in a physical medium", is that code _does things_, in a way different from previous forms of creative expression fixed in a physical medium. Copyright is a weird edifice to begin with, and code makes it weirder, for sure.
> APIs are no different from any other code.
To me, API's are _not code_ at all, sot that's why they are different from "any other code." An API is a _description of code_, not code itself. Code implementing an API is surely copyrightable, but it seems to me clear that an API -- the description of classes, methods, and signatures -- is not code, it is a description of features of code. Google here lost by making code that _worked the same_ as Sun's, not because they copied Sun's Java source. And that's why it seems clear to me that it ought not, consistent with previous copyright law, to be copyrightable.
But clearly people will disagree, especially non technical people, which is why this is a case. I think most technical people tend to agree with me, but obviously not all.