Amber is a suite of biomolecular simulation programs. It began in the late 1970's, and is maintained by an active development community.
The term "Amber" refers to two things. First, it is a set of molecular mechanical force fields for the simulation of biomolecules; these force fields are in the public domain, and are used in a variety of simulation programs. Second, it is a package of molecular simulation programs which includes source code and demos.