Official Cube Description:
Cube is an open source multiplayer and singleplayer first person shooter game built on an entirely new and very unconventional engine. Cube is a landscape-style engine that pretends to be an indoor FPS engine, which combines very high precision dynamic occlusion culling with a form of geometric mipmapping on the whole world for dynamic LOD for configurable fps & graphic detail on most machines. Uses OpenGL & SDL.
Cube is a Doom-like first person shooter. THe graphics are very well down for a free Open source game. The general game play for Cube is very simple. The game started in edit mode but there are numerous single and multi-player maps. For further information be sure to read the Cube documents and other information that comes along with the free download. The official page is a great place to start. The free download is available from Sourceforge.net
The 2 Downloads from 2003_12_23 are the most recent. I only downloaded cube_2003_12_23.zip and had no trouble installing.