Depends which country you're from. Gnutella is P2P = peer to peer. Sharing from one to another. If you're simply a leech & want to take but not give back then that's your prerogative. If nobody shared ... leeches would be out of business as would be everyone else for downlding.

Legality is a big topic. I'm not about to start upon it! But if you download copyright material ... do you seriously think that is legal? As said it depends upon your local laws. There's no laws against sharing or downlding here as of yet!