RMS on Copyrightability of APIs

It would actually be more like allowing someone to have a copyright on Klingon or Esperanto. APIs and constructed languages were at least created by a particular individual or organization, and have a certain amount of arbitrary choice. If there are a lot of fields and methods that aren't determined by any fixed scheme, that aspect could be copyrightable. If there are quirks of the API which are only necessary for interoperating with that particular implementation, those probably are copyrightable. In general, APIs should probably be copyrightable to the extent that they are poor APIs.