Gala is a Python package for Galactic and gravitational dynamics.
The easiest way to get Gala is to install with pip:
pip install astro-gala
See the installation instructions in the documentation for more information.
Prior to May 2016, this package existed on GitHub as "Gary". I would recommend that you update your code to instead use this new package, Gala, but if you don't need any new functionality and are ok with no support, that code still exists here.