Most of the critical parts of FAH are publicly available. The Tinker and Gromacs source codes can be downloaded and run. Unlike many computer projects, the paramount concern is not functionality, but the scientific integrity, and posting the source code in a way that would allow people to reverse engineer the code to produce bogus scientific results would make the whole project pointless. However, we stress that the vast majority of our code is already open source. We have an Open Source FAQ with more details.
