Envy is described as 'P2P Filesharing and BitTorrent client. Polished dev fork of Shareaza supporting Gnutella (LimeWire), G2 (Shareaza), eDonkey2000 (eMule), and more networks. Highly customizable, skinnable, and translatable with 30 languages' and is a Torrent Client in the file sharing category. There are more than 25 alternatives to Envy for a variety of platforms, including Windows, Linux, Mac, BSD and Android apps. The best Envy alternative is qBittorrent, which is both free and Open Source. Other great apps like Envy are Transmission, µTorrent, Deluge and Free Download Manager.
Vuze (formerly Azureus) is a free BitTorrent client used to transfer files via the BitTorrent protocol. Vuze is written in Java, and uses the Azureus Engine. In addition to bittorrenting, Vuze allows users to view, publish and share original DVD and HD quality video content.
aMule is an opensource alternative to eMule : aMule is a free peer-to-peer file sharing application that works with the EDonkey network and the Kad Network, offering similar features to eMule and adding others such as GeoIP (country flags).
A fork of the qBittorrent bittorrent client with enhanced features.
MLDonkey is an open source, multi-protocol, peer-to-peer file sharing application that runs as a back-end server application on many platforms. It can be controlled through a user interface provided by one of many separate front-ends, including a Web interface, telnet interface...
Shareaza is the most luxurious and sophisticated file sharing system you'll find. It can harness the power of up to four separate peer-to-peer networks, including EDonkey2000, Gnutella, BitTorrent and Shareaza's native network, Gnutella2.
Fopnu is P2P File Sharing System. 100% Free, Simple and Easy to Use. Contains NO Spyware and NO Ads. Fully decentralized network. All shared files are indexed locally.
DC++ is an open source client for Windows for the Direct Connect protocol. Direct Connect allows you to share files over the internet without restrictions or limits. The client is completely free of advertisements and has a nice, easy to use interface. Firewall and router suppor.
Halite (named after the mineral) is a C++ BitTorrent client based on the excellent libtorrent library from Rasterbar Software. The program also relies heavily on the Boost libraries.
kMule - short form for "kad mule" - is intended to be the most lightweight eMule compatible client out there. While eMule does a great job, it may contain too much bloat for the everyday user and it's updated not often enough to respond to the users wishes.
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The original source that was forked and continued.