Libpurple
Libpurple (ex libgaim) is the name of the software Bibliothèque of communication by Instant messaging created by Pidgin (ex Gaim) and written in C. It is available under license LPG and used by many other software of which Adium, Fire, Meebo, Proteus and WengoPhone. Libpurple was obtained thanks to the refactoring and with the separation of the user interface of the part of the code managing the interface with the other transport.
Libpurple supports the protocols Jabber, IRC, SIP, Hello (Zeroconf), AIM, Gadu-Gadu, ICQ, MSN, Yahoo! IM and Zephyr.