After negotiations between different BitTorrent developers a new proposal was written and then implemented into the Azureus and µTorrent betas within days.
Some clients, like ABC, Vuze, BitTornado, TorrentStorm, and µTorrent have a "super-seed" mode, where they try to only send out pieces that have never been sent out before, theoretically making the initial propagation of the file much faster.
Other seedboxes are special purpose and run a variety of torrent specific software including web interfaces of popular clients like Transmission, rTorrent, Deluge, and μTorrent, as well as the TorrentFlux web interface clients.