Downloading is free. After that... here's what I ask.
If you use this piece in your game, film, play, art project, penguin sanctuary, or other creative work, please contribute the amount you deem fair, based on what you feel you can give, and based on how you use it. I trust you. If you're a broke indie-dev/student/etc. and you happen to scrounge up 5 bucks to toss my way, I'll be honored (and I'll probably use that money to buy you a beer/coffee/tea/smoothie next time we run into each other.)
If that creative work really takes off, maybe pitch in a little more. Or, you know, hire me next time as your music person. Or tell your new rich buddies to come find me. Or not. I'm mostly just happy to get this stuff out there.