Check out PyWeek 12’s winners by the way:
Loopback: Asteroids + Tower defense. Retro Look. Permissive code license.
Loopback – PyWeek #12 Team Winner
Lemming: Enough Plumbers + Canabalt??? Hand-drawn horrible ;). Permissive code license.
[youtube https://www.youtube.com/watch?v=BOkXWp4OLsM&w=460&h=245]
The PyWeek guys seem to have figured out the license part of game prototyping well: Lemming for example contains a list of all used art pieces’ urls and licenses. Neat!