I am involved in and maintain (with varying degrees of diligence) a few different codebases with interesting physics applications:
I am part of the GAMBIT collaboration, a group of intrepid parameter space explorers. I didn’t write the code, but I can tell you how to get Gambit to run on OSX (Mojave).
Captn’General is a Fortran standalone code (and GAMBIT backend) to calculate the velocity and momentum-dependent capture rate of dark matter in the Sun.
nuFATE: Neutrino Fast Attenuation Through Earth, is a rapid python (C++ and Matlab now also available) code that compute the attenuation of high-energy (> TeV) neutrinos as they travel through the Earth (details in arXiv:1706.09895)