DIVE INTO SOFTWARE / PEER-TO-PEER /
gnucleus
John Marshall and others
http://www.gnucleus.com
Win / *nix
GPL
Gnucleus is a Peer to Peer file sharing system for Gnutella networks. Its fast, free and doesn't include spyware or adware or other hidden nasties that are common in P2P clients these days. It also makes it very simple to set up P2P systems on non-internet-connected networks which makes it a good choice if you want to do an off-line file sharing system with a group of friends or the people in your local Free Network.