I will start by telling how tuxracer has evolved, When it was anounced that tuxracer was going commercial, 3 different projects continued the opensource version of tuxracer: ppracer, openracer, & penguin-racer. Penguinracer never got started, AFAIK. OpenRacer is still going, but has only released multimedia packs to be applied to the original game. PPRacer released 2 working version of the game with many enhancements (0.31 & 0.5a), but it to has ceased to excist.
A new group of developers has started to work on ppracers sourcecode, and has recently released the first version of ExtremeTuxRacer, it looks very promising, and is fully playable. Multiplayer is still in the works and is not available. The game can be configured from the menu to be controlled by the keyboard or an HID, a gamepad oor joystick. The menu is a mouse driven GUI. The joystick button setup requires a bit of guesework, it is easier if you have a gamepad with numbers on the buttons (logitech cordless rumblepad is good) if you do have numbers, remmber that button #3 is probably #2.
Even though I am on a mac, I am running the windoze version of ET Racer with parralels. The source is available along with linux and windows binaries. The source probaably compiles under MacOS X. The 0.5a source of ppracer comppiled cleanly on MacOS X, and ET Racer is based off ppracer.
Unlike the 1.0 version of tuxracer, all the coarses are available to play on without wining an race against an AI player.There are 5 or 6 different types of collectables and many dfferent terrain types ranging from ice and snow to lava and rock. There are no moving object or caves in the tracks.