Gnucleus is a popular Gnutella client for the MS Windows platform, released under the GPL license. The primary goals of the project are security and stability. The client is designed to be easy to use without reducing the number of options available. Gnucleus implements a number of advanced features including Ultrapeers (Gnutella nodes that aggregate an index of files on child nodes to shorten search paths), multisource swarming downloads, SHA1 file hashing, and partial-file sharing.

Recently the development picked up some steam, introducing tiger-tree hashing, proxy support as well as support for the Gnutella2 network.

The network core, now dubbed GnucDNA, has been separated from the main programm and is being used by many other Applications such as Morpheus and Nova.

Project homepage: http://gnucleus.sourceforge.net