Frostwire - File sharing program that connects to the same network as Limewire, except it is free and contains all the features as Limewire pro.
Also, read this (very interesting):
The project (this program) was started in September 2005 by members of the LimeWire open-source community, after LimeWire's distributor considered placing "blocking" code which it was developing in response to RIAA pressure and the threat of legal action in light of the U.S. Supreme Court's decision in MGM Studios, Inc. v. Grokster, Ltd. When eventually activated, the code could block its users from sharing licensed files. FrostWire was first released in October 2005.
