GTK+ is a highly usable, feature rich toolkit for creating graphical user interfaces which boasts cross platform compatibility and an easy to use API. GTK+ it is written in C, but has bindings to many other popular programming languages such as C+, Python, Perl and C# among others. GTK is licensed under the GNU LGPL 2.1 allowing development of both free and proprietary software with GTK+ without any license fees or royalties.
See GTK for more information.
Pidgin (previously Gaim) is a GTK2 based instant messenger application, it’s widely used and supports a wide array of IM services. This works as a great replacement for closed-source IM clients.
Pidgin versions are available for all major operating systems, including Windows, Linux, FreeBSD and Unix variants that run X. On OSX however it is recommended to use Adium, as this is written to run natively on OSX and uses the same core engine, libpurple (previously named libgaim.)
IM
Gaim
Client
gtk2
License:GPL
open
Jabber
replacement
gtk
gtk++