Actionscript Physics Engine - APE

APE (Actionscript Physics Engine) is an AS3 open source 2D physics engine for use in Flash and Flex. It’s continuation of the long dormant AS2 Flade project. APE is written and maintained by Alec Cove.

CircleParticles
- fixed or non-fixed
- variable mass, elasticity, and surface friction

RectangleParticles
- rotatable
- fixed or non-fixed
- variable mass, elasticity, and surface friction
- corner particles that can be attached to other particles with SpringConstraints

WheelParticles
- traction and angular velocity
- fixed or non-fixed
- variable mass, elasticity, and surface friction
- edge particles that can be attached to other particles with SpringConstraints

SpringConstraints
- stiffness
- collidable or non-collidible
- collidable constraints have variable width and scale

Licensing
- non restrictive LGPL

See APE site here.