I think he won't be against it, but well I also think that he may not go on this site untill a long time and he may not even see this topic, so you should just use his songs, mentionning the titles and the author somewhere in your map, or idk.
How would you like your name to appear in the credits do you want it as Green House Productions?
I'll let you know when I have it finished or demo ready it's going be at least a few months, gunna try to have it out on the new console (coming around 2013) as a android game. But the Windows and Mac versions might come out before then because I have to make it a little differently for the android cuz of controls being different. I have just started pretty much me and my brother just been writing up story ideas and characters and stuff they will do, haven't done any of the coding yet, so still have a ton of work to do.. I think our ideas are going to be great we are leaning towards a 2 plat-former right now with lots of game play unlike any other game.