There are currently three major versions of the code.
The “old” code: http://grandcentral.apam.columbia.edu:5555/principia_materia_doc_v0/
The “new” code: http://grandcentral.apam.columbia.edu:5555/pmdocs/
The “development” code, which is documented here. The development code is currently a branch of the new code, currently named dev/only_phonons.
The new code and the development code are here:
https://github.com/marianettigroup/principia-materia
The old code is here: