Pidgin

Preferred license: GNU General Public License (GPL)
Pidgin is an open-source, cross-platform, multi-protocol, instant messaging library (libpurple) and clients (Pidgin and Finch). It supports numerous IM protocols with a single unified interface, abstracting away the concept of multiple IM services.
Actual source code produced by the student participants in Google Summer of Code™ for Pidgin can be found here.
 
Current Projects
by Jeffrey Connelly, mentored by Sean Egan
by William Ehlhardt, mentored by Ethan Blanton
by Will Thompson, mentored by Robert McQueen
by Eric Polino, mentored by Sadrul Habib Chowdhury
by Eoin Coffey, mentored by Gary Kramlich
by Carlos António Vieira Silva, mentored by Mark Doliner
by Prekshu Ajmera, mentored by Richard Laager
by Shkutkov Michael, mentored by Richard Laager