BitTorrent only works as long as at least one peer has the bits you need. The only way to insure that is to host a permanent seed. The Video Toaster sources do not share the same level of popularity as World of Warcraft or Lady Gaga, so in all likelihood, Bill would have to seed the ISO image indefinitely. In any case, he's already said bandwidth charges weren't the impetus for the change, although he certainly implied that at the beginning. ;-)
EDIT: Mini-rant not directed at anyone in particular: We all pay for bandwidth, and the only "winners" are the large telcos, who whine whenever anyone tries to use the bandwidth that's already been paid for.
I see where you were going. I was thinking/suggesting the community does the seeding and the OVT site could still have the regular download too. Many sites I've seen that need large bandwidth for something like this usually have the bittorent link listed first with a message asking to please use that if possible. Then the standard http/ftp download option listed a little smaller and second.
The message had said they paid over $300 in a single month for bandwidth overages. So in effect they'd still have the file for those that don't want to use the torrent, but we would be helping relieve that overage. Hence in effect donating $300+ a month.