Re: This article conflates two important issues
But "the actual text written to explain these rules" has no creative content. It is either an accurate statement of those rules or it is not the API. Does US law permit someone to claim copyright on facts? (Honest question, btw. The law is such an ass that it might well do. As far as I know, the law in the EU stems from a directive that specifically permits such reverse engineering as is necessary to permit interoperability. That would, by definition,apply to an API.)
On the other hand ... The rules may well have resulted from a huge creative effort on someone's part. Getting the API right might be most of the work on some projects. The wrong API produces a crap product and the right one produces something that everyone acknowledges to be a work of genius. The actual implementation might be trivial.