FrostWire is a free, open source

Free and open source software

Free and open-source software or free/libre/open-source software is software that is liberally licensed to grant users the right to use, study, change, and improve its design through the availability of its source code...

 BitTorrent client first released in September 2004, as a fork

Fork (software development)

In software engineering, a project fork happens when developers take a legal copy of source code from one software package and start independent development on it, creating a distinct piece of software...

 of LimeWire

LimeWire

LimeWire is a free peer-to-peer file sharing client program that runs on Windows, Mac OS X, Linux, and other operating systems supported by the Java software platform. LimeWire uses the gnutella network as well as the BitTorrent protocol. A free software version and a purchasable "enhanced"...

. It was initially very similar to LimeWire in appearance and functionality, but over time developers added more features, including BitTorrent support. In version 5, Gnutella

Gnutella

Gnutella is a large peer-to-peer network which, at the time of its creation, was the first decentralized peer-to-peer network of its kind, leading to other, later networks adopting the model...

 support was dropped entirely, and FrostWire is only a BitTorrent client. Development of the program has been active since the program was first released in September 2004.
The project was started in September 2004 after LimeWire's distributor considered adding "blocking" code in response to RIAA

Recording Industry Association of America

The Recording Industry Association of America is a trade organization that represents the recording industry distributors in the United States...

 pressure.