LW is a peer-to-peer application which allows users to connect to the Gnutella network for file sharing. You can download files which other users are sharing & they can download files that you're sharing. Click on the links below for more info.
Gnutella - Wikipedia, the free encyclopedia

LimeWire - Wikipedia, the free encyclopedia

Lime Wire » About Using P2P Software Safely


Files downloaded using LW are free, but that doesn't mean that there aren't copyright violation issues - depending on where you live & what laws are in place.

Use the forum search to look for legal, legality or something similar...you'll find lots of old threads to read through. Searching with Google will help you to find out your local laws