Irrlicht

A free Game Engine / SDK that implements quake models and maps. Open source and not GPL.

Irrlicht Engine Home

Here you can get the Irrlicht source and examples.
• http://irrlicht.sourceforge.net/

Cpan Irrlicht section

This has some code and examples for use with irrlicht.
• http://search.cpan.org/~tels/Games-Irrlicht/

Irrlicht Tetris

A tetris game made with the Irrlicht game engine.
• http://www.technomagicum.net/projects/IrrLicht/tetris/