Might I suggest we follow the pattern of text structure in .content field for license and don't add another tag? There are no existent concept of license in tags in any Nostra event and we already have clients that does "Credits:" and "Lyrics:".

So I suggest we parse license from the text content:

"License:

Creative Commons CC0"

It means you can't query for a license with the relay. Also if we wanted to do indexing, license names would need to be standardized.