The philosophy of our Research Group is to make all software (eventually) open source and freely available. Below is a list of currently available open source software.
A code to model the secular (long-term) dynamical evolution of hierarchical multiple systems composed of nested orbits, with an arbitrary number of bodies and structure. Tides and relativistic effects are also included, as well as the effects of flybys and supernovae. The technical details can be found here, here, and here. A standalone version (implemented in C++, with a Python user interface) can be downloaded at https://github.com/hamers/secularmultiple. You can try out the code online (without installation) for a few select (planetary) configurations here.
Test Particle Integrator
A C++ code to compute the gravitational dynamics of particles orbiting a supermassive black hole (SBH). A distinction is made between two types of particles: test particles and field particles. Field particles are assumed to move in quasi-static Keplerian orbits around the SBH that precess due to the enclosed mass (Newtonian "mass precession") and relativistic effects. Otherwise, field-particle-field-particle interactions are neglected. Test particles are integrated in the time-dependent potential of the field particles and the SBH. Relativistic effects are included in the equations of motion (including the effects of SBH spin), and test-particle-test-particle interactions are neglected. Download: https://github.com/hamers/tpi.