An OpenGL user interface written in C++ some time ago. It is not maintained anymore and it's here for reference.
The project is portable and can be compiled on both Windows and Linux platforms. The class structure follows very close the famous Borland C++ Builder UI controls. The graphics engine is loose coupled with the controls and the interface can be used as stand alone applications or inserted in existing game engines.
The project's goal was to allow developers to create OpenGL UIs that looked similar to the desktop versions like OSX.
Windows / Linux
MIT License