"publish the API" - "enforce control"
That's exactly what copyright is for . make something available to the (paying) public without losing control of it.
IMHO the problem here is if an API signature (and the whole body of APIs signatures that makes up a whole library/framework) is copyright-able or not.
This is not a little issue, because we'll see a big fight among companies that kept most of all their coding inside (often taking advantage of someone else work) and publish relatively very little and non-core (Google) and others who develop code/tools to be reused by others and thereby publish a lot more, and "core" assets as well.
People siding with Google should think about the impact it could have on licenses like the GPL also - i.e. Microsoft would be free to clone the whole Linux API ignoring the GPL.