Apparently, Sorenson 1 has been reverse-engineered and you can play it with Mplayer. Sorenson 3 is apparently still in the works. Conveniently (if you happen to be an x86 user ;) ) they have a mechanism to play Sorenson 3 encoded files using Windows DLLs.. however, obviously this will not work on a PPC.
Has anyone here figured out a way to play Sorenson 3 encoded QT files under Debian/PowerPC?