Recently I decided to tackle getting torrent software loaded on the ATV. I found a reference at Awkwardtv.org. Got it running yesterday using rtorrent from http://code.google.com/p/rtorrent-appletv/. The program was noted on awkward tv at http://wiki.awkwardtv.org/wiki/How_To_Install_rTorrent. At the bottom of the page it says Where to Get rTorrent for AppleTV. That is the link to the code.google page.
The project owner is not the author of the program. He has compiled the open source code for the torrent software for the AppleTV. The sofware seems to work great. I am no expert at this. I just got it running but with the software and the screen utility, so far (one day of use) so good.
For the users guide and ongoing discussion…the original author of the open source code, forums and more can be found at http://libtorrent.rakshasa.no/wiki. Mind you the support there is for the software… not the software running on the Apple TV.
Best to all,