OpenMM is a toolkit for molecular simulation. It can be used either as a stand-alone application for running simulations, or as a library you call from your own code. It provides a combination of extreme flexibility (through custom forces and integrators), openness, and high performance (especially on recent GPUs) that make it truly unique among simulation codes.
Need help using OpenMM? There are several places that you can find it:
OpenMM is free and open-source software. There are several licenses which cover different parts of OpenMM, but most of the source code is covered by the MIT license or the GNU Lesser General Public License (LGPL). Portions copyright © 2008-2025 Stanford University and the Authors. For more details, see Licenses.txt.