While it is unpopular among most HN readers that APIs be found to fall under copyright, I don't see how it affects software interoperatability in the long term.

While it is unpopular among most HN readers that APIs be found to fall under copyright, I don't see how it affects software interoperatability in the long term. It seems to me that all that this necessitates is for software publishers to include an open license for their APIs, or to release it into the public domain. In fact, it might even be beneficial, since companies can license different APIs to different customers, and have additional legal force prohibiting the use of APIs that are unofficial or unauthorized to them.