SuperTuxKart
Kart racing with power-ups, battles and split-screen play.
Credits and licenses
Prism lists this game from its makers' open source. They aren't affiliated with Prism.
SuperTuxKart 1.5
Code
Art and sound
mixed: CC-BY-SA-3.0/4.0, CC-BY-3.0/4.0, GPL, CC0, public domain and OFL-1.1 fonts, with some assets of unclear provenance; see data/licenses.txt and each asset folder's licenses.txt