glad you asked.
now there's a proper client available for 10.3, and it actually works now. you can get that from VersionTracker.
there are also 'unofficial' clients, i don't really know what the difference is.
to download stuff via BitTorrent (BT) you first download a .Torrent file. then you open that file in BT and it connects to peers and you start to download. you also have to upload at the same time, this is how it works, and how everything gets spread around. you can limit your UL's but then i think it also lowers your DL speed.
here's a link to get you started DL'ing:
RedVsBlue.com. RVB has some Blood Gulch episodes that you can DL by BT.
and yeah, Google is your friend.
