Just because it's free doesn't mean it's legal. Technically it's a broadcast of copywritten infringement. Without paying royalties (7 cents per song and licencing fees in the hundreds) Whether they go after me is a diffrent concern, but with PokeMMO in it's legal grey area, I want to be safe, it's not quite fair use at that point.
Some services will pay the fee, but their cheapest package with being able to play copywritten music (with the sucky Live365) is about 150/month so that's obviously out of my budget.
I'm gonna hunt down some free music to play (stuff like Weird Al's You're Pitiful, or maybe some gaming remixes) and I need to buy a mic to do this, but I'm looking (If I don't get too busy with work) Maybe October 1st as a first test stream.
Edit: I'm loving creative commons, non-commercial music. This could be fun :)