Re: metadata: I suspect that it may indeed be already incidentally covered by existing licenses. I replied elsewhere with a link to this wikipedia page: https://en.m.wikipedia.org/wiki/Structure,_sequence_and_orga...

The SSO of a piece of software is called a "nonliteral element". Just speculation on my part here, but I'd bet that version history might fall under this "nonliteral element" part of copyright law.