One of the issues here is that it's not even clear under which license the API should be covered. Does the existing software license also cover the API, or must it be explicitly defined?
What happens when an API is co-created by different software developers which each creates their own software under different licenses, through communications which themselves aren't explicitly licensed (like over email lists), and then summarize what they agree on in text instead of code (like the RFC process)?
At no point have either one of them explicitly given permission to use their respective contributions under another license. Even if they agree that the RFC text is public domain, that technically do not extend to implementations of the API which it describes (as those are different works!). And there exists no official reference code with legal approval from all contributors, whose license could be adopted by other developers.
