Penguin Planet Racer (site) is a free open source update of the TuxRacer game. Version 0.5 alpha was released a few days ago which includes experimental multiplayer support.

I just compiled a copy (you’ll need to download the source code and compile, it’s not in Portage). Once you’ve done that, start the program using the command ‘ppracer –multiplayer’ and try practice mode. You get one black penguin and one blue one

I presume the other penguin is controlled by the computer as it seems to move by itself. I can’t seem to lose against it though