The Steem blockchain does not provide a field to store the license given to a track/song. A shame, a Flaw even of the Steem blockchain IMHO. You could take the approach you take, always mention license offered in the post. You could also take the approach you only mention the license in the post, when you somehow restrict the use of your material. Although I'm not a musician, therefore I don't upload music at all, I would prefer the suggestion of always including the license terms in the same post as you post/share the music with. That makes it clear at all times for everybody :)