making music or even choosing music is always hard, i mean you can allways load some britney spears or mettalica tune to your game but they can sound a bit odd
You need to remember what kind of music you're after - obviously for dark and gloomy games you need something that sounds diffrent then for funny colourfull "bunny adventures" game. lol
rip music? you can always rip music (but rip carrefully)
compose? sure. more experience you have better music will be.
licensed track are always trouble - you can try to ask that music track owner if you could use his song in your game (it's free game, non profit etc.)
but what i recomend is to try compose something by yourself - internet if full of free and good music software - and it's not that hard really.
sometimes only few sound in background fit perfectly to game.