Which is the most advanced GPLd OpenGL FPS 3D engine today, even if in Beta version?

By "most advanced" I mean support the most and latest and greatest OpenGL graphics features.

By GPL I mean GNU Public Licence (v2, v3 etc), and not free as in gratis but closed source.

By FPS I mean First Person Shooter, as in Quake, Quake 2, ioquake, Nexuiz, Sauerbraten, Urban Terror, etc.

For this particular question I am not interested in physics or AI. Those aspects could have been a separate questions.