gnutella (the protocol) is used for searches. Once the sources are discovered, HTTP is used for the file transfers.
So, for better answers from developers, try the Phex forum, the gnutella developerrs
the_gdf : The Gnutella Developer Forum (GDF) or see
LittleShoot -- P2P 2.0 -- P2P File Sharing in the Browser and of course
LimeWire Forums