What it is:
fast-paced 3D first-person shooter. OpenArena is an open-source
content package for ioQuake3 licensed under the GPL, effectively
creating a free stand-alone game. Though OpenArena is a free
replacement for id Software Inc.’s Quake 3 Arena, it is NOT compatible
with the proprietary game!
OpenArena might be considered unsuitable for children.
To know more about:
To install in Ubuntu:
sudo apt-get install openarena