Gnutella is the name of the network. Limewire is simply one of the clients that are designed to run on the Gnutella network as you can see if you view the entire forum. No this is not a LW specific forum but a very large proportion of the forum is dedicated to LW. The LW forum section is here:
http://www.gnutellaforums.com/forumd...p?s=&forumid=7
As for Privacy from corporations such as riaa, etc. It is highly recommended that every user of p2p apps arm themselves with Peerguardian
http://peerguardian.methlabs.org/pg2.html (FREE) (as well as anti-virus, adaware, spyware.) PG will block out those companies trying to approach upon your computer via the net.
Napster (to my understanding) used a central server which means all files were offered from one site. Gnutella does not offer that. It is simply p2p (Peer to Peer) which means its people like you, your next door neighbour or somebody over the other side of the planet sharing files from their location.
As to sharing copyright material, well that's an individual's decision. It depends on each person's national laws as to whether this is illegal or not. There is a lot of non-copyright material being shared, but there is also a lot of copyright material being shared. What you decide to share or download is up to you. If you do a search of the forum then you will find this topic has been discussed many times before. Search for legal or illegal or riaa.
I'm sure that over the next few days there will be other members who can give you a better description & explanation.