Static and Dynamic Structural Analysis of 2D and 3D frames.
FRAME3DD is a program for the static and dynamic structural analysis of two- and three-dimensional frames and trusses with elastic and geometric stiffness.
IBDS is a library for dynamic simulation of multi-body systems in C++. It simulates rigid bodies, particles, many different joint types and collisions with friction.
(ZLib license, free for commercial use)
More infos: http://www.impulse-based.de