Rolando sources

Through some digging around I found that ngmoco's Rolando "platformer" game uses the Box2D physics engine. Box2D is open source, but doesn't have an iPhone port. Since Hand Circus used this open source and modified it they must release the modifications under the GPL. One of the changes they made was to accept accelerometer input for a general force vector on all objects in the simulated world.

The sources are available here:
http://sourceforge.net/projects/box2d

It's not Rolando, but the demonstrations of the Box2D physics engine are inspiring for new game ideas.