The technology used for UDP communication is MFP, provided by Amicima. Developer documentation can be found here :
MFP library is licensed under GNU General Public License (GPL). Custom changes made to MFP library by AllPeers are listed in CVS in allpeers/p2p/mfp/mfp_3rd.patch and allpeers/p2p/mfp/mfp_3rd_patch.README
MFP can be configured by adding following lines to prefs.js :
Instructions on how to test MFP and NAT traversal are [:Testing_MFP: here].