I love your music <3 :)

By the way, about the licenses you have chosen: You don't need the CC-BY license together with the CC-BY-SA license. SA means Share Alike, so that people have to release their modifications of your music under the same license again. CC-BY means that people can do whatever they want with it and only have to mention you (like they always have to at Creative Commons), even make commercial stuff with it. You see, these licenses bite each other. With CC-BY you allow people to do whatever they want with it and with CC-BY-SA you restrict them to release their stuff under CC-BY-SA again. So it's fine to have the SA license if you need that as it already contains the CC-BY one. Also, i don't know how the GPL goes with that, i only know how Creative Commons works...

Excellent!

@Cynic Project:

A dreamer wandering through the clouds, perhaps. Straightforward, clean, and effective. Well done, Alex.

@Bonsaiheld :

That's correct; there's no particular reason to dual license under both CC-BY and CC-BY-SA. The former, being a more liberal license but otherwise identical, essentially supersedes the latter. There's no real harm done in issuing excessive or extraneous licenses, though.

As for GPL, that would be totally independent. GPL is not recommended for artistic works (only programs and libraries). The reason for that is it's not legally clear how the source code provisions of the GPL would/should interact with artistic works. However, the author would have to do a GPL grant if you wanted to include something into a derivative work that is only licensed under GPL and nothing else.

Something else that should probably be mentioned about CC-BY-SA is that there isn't a completely standard interpretation of what "Share Alike" is supposed to mean in terms of exact law and precedent. On the one hand, it's pretty clear that for a Share Alike work, you need to release any derivative works under the same license.

However, what constitutes a derivative work? For some items, like movies, it's generally agreed that a movie which incorporates a piece of music is a derivative work. The movie is synchronized in a very particular way to that music, so it's a relatively obvious call. For a game that uses a music track, it usually would be thought a derivative work, but not always. If the connection between the game program and the music is very loose, a court may end up ruling that the two are a "mere aggregation" rather than a derivative work, and thus the Share Alike provision would not come into play for an unaltered music track. That probably sounds confusing, but it may be clearer if you think of the game as a music playing application rather than an artistic work. For a music player, what song it plays is pretty arbitrary (it could be anything) and the code doesn't necessarily care in any meaningful way. Thus, in some contexts it's possible to end up with a situation where there isn't enough artistic interaction between two things for the derivative works aspect of copyright law to come into affect. Though overall, the line between an aggregation of separate works and a derivative work is very fuzzy in the law and can easily differ from case to case.

Personally, I would recommend that people refrain from using CC-BY-SA works in closed source programs for two reasons. One, a lot of the people using that license intended any CC-BY-SA to force any client program to be open source (they see it kind of like an artistic GPL, basically). Two, there's a good chance that a court would rule many common uses to be derivative works because of the degree of synchronization that is often used in games between the gameplay and the music tracks (sort of similar to movies).

Likewise, for authors and artists the Share Alike license makes more sense if you intend your work to be used only in conjunction with open source programs. Some specific types and use cases of closed source programs might be able to get away with using your work anyway, but there's not much you can do about that. (In any case, the bigger problem is people who ignore licenses completely.)

Note that a lot of authors and artists may be perfectly willing to sell you a CC-BY or other similarly liberal license for an affordable fee. It never hurts to ask.

One last thing to mention is that all of the licenses allowed on this site permit commercial use (sale) of resulting products, whether they qualify as mere aggregations or derivative works. So it's really only a question of whether programs ought to be open source or closed, rather than whether they're noncommercial or commercial. Watch out for the Creative Commons noncommercial and no-derivatives licenses on other sites, since those can be very tricky to deal with.