I love this idea. You could webseed just in case there's no one currently seeding (I guess it's something Humble Bundle is doing with their torrents). Keep it a private, non DHT server (something like gameupdates.org is doing). I'd certainly seed the stuff I've downloaded. As it currently is, those archives just sit there, on my HDD, unused, so someone could use my bandwidth to download them and spare your servers a little stress.