Okay, i didn't word that real well. I do know how APIs work, although i haven't done any programming yet in 10.5. My point really was that utorrent doesn't *require* anything not present in 10.4 (or perhaps even earlier). Thus, you could easily make it work in 10.4. The more compatible a piece of software is, the better. It is true that companies like Adobe and others constantly push the OS envelope, forcing people to always have the very latest upgrade, but they have a vested interest in profit, as does Apple. Open source type software ought to be doing the opposite. :/