qt-x11-2.2.4.tar.gz or later version
Qt is a cross-platform GUI library that makes it easy to create X applications with standard GUI elements (widgets) like menubars, scollbars, dropdown lists, checkboxes, buttons, multiple document interface, and many other GUI things. Using Qt, a program can be compiled for both MS Windows and X without changing any code. Its a very popular GUI library and is used to create the core libraries of KDE (http://www.kde.org/).
Qt has functions (previously as an extension in $QTDIR/extensions/opengl) for OpenGL that provides for creating OpenGL rendering contexts in Qt windows. This provides some alternative to both GLUT and using the glX functions directly, plus the added benefit of full access to the excellent Qt widgets and cross-platform portability.
This is useful if you want to compile or develop programs based on Qt (e.g., KDE2 and its apps).