THOR is now open-source on this link.
THOR is a flexible Global Circulation Model (GCM) that solves the three-dimensional non-hydrostatic Euler equations on an icosahedral grid, and was designed to run on Graphics Processing Units (GPUs). THOR was developed from ground-up with the propose of exploring a large diversity of planets and avoiding physical approximations brought from other research fields. This model has the capacity to simulate 3D virtual atmospheres coupling the physics self-consistently.
A detail technical description of the model can be found here.