Open Sourced, Multi-Protocol, Compressing Proxy?

dotd asks:"Are there any open source alternatives to Fourelle's Venturi. It compresses HTTP, FTP, SMTP, IMAP, POP, and NNTP and sends it over a UDP connection to a Venturi server. It is especially useful for satellite networks where UDP seems to improve the 'felt' latency, (vs TCP and a compressing proxy like RabbIT) however it requires a proprietary client and server. Coincidentally, the Venturi box runs Linux (kernel 2.0.36), and boots off an 8MB SanDisk. It also runs Squid and ssh. "