Jeff Steel I posted about licensing the music before, and I want to revisit that.
Looking at the credits, I see credit for the music - Kevin MacLeod, licensed under Creative Commons. What I don't see is credit for the vocals. It looks like the vocals are used without permission. This may or may not be true.
This should be cleaned up. The vocals are very important, and releasing the game with them in without a license makes you guys dirty pirates just like us.
I think you guys should release this game on steam. But to do that, you really need to fix the music license issues.
If the vocals are licensed, you should still credit the vocalist.