pidgin  2.11.0
About: Pidgin is a chat program (multi-protocol instant messaging client) which lets you log in to accounts on multiple chat networks simultaneously (old name "gaim").
  Fossies Dox: pidgin-2.11.0.tar.gz  ("inofficial" and yet experimental doxygen-generated source code documentation)  

Pidgin/Finch/libpurple API Documentation

libpurple is intended to be the core of an IM program. Pidgin is a GTK+ frontend to libpurple, and Finch is an ncurses frontend built using libgnt (GLib Ncurses Toolkit).