Google says API’s can be copyrighted now. I thought the oracle case was ongoing:
> Additionally, the Git repo contains several files that violate Google’s copyrights:
Google license_protcol.proto (see Google copyright at the top of the file): /widevine-l3-
This doesn't claim that they're infringing on the copyright of their API, rather that they infringed on their copyrighted code (even if the code is just declaring the API).
It's fairly unlikely that someone would reimplement the API and then add in a Google copyright header. It's pretty clear that it was directly copied.
> Additionally, the Git repo contains several files that violate Google’s copyrights: Google license_protcol.proto (see Google copyright at the top of the file): /widevine-l3-