GTK+ is a multi-platform toolkit for creating graphical user interfaces, primarily designed for the X Window System. 

GTK+ is free software and part of the GNU Project. However, the licensing terms for GTK+, the GNU LGPL, allow it to be used by all developers, even those developing proprietary software, without any license fees or royalties.

For more information look at: http:www.gtk.org

The DLLs included in this package have been borrowed from http://www.libsdl.org/Xmingw32/
