1 What is PyMOL? PyMOL is an open-source molecular visualization system built on an open-source foundation. That means you get free access to source code--hence 'open source.' Schrodinger compiles and sells ready-to-run binaries for Windows, Mac, and Linux (http://pymol.org/buy). 2 Source Code You can download the open-source code from github: https://github.com/schrodinger/pymol-open-source 3 Legacy Builds To support the PyMOL community, Schrodinger provides access to some PyMOL legacy builds at no-cost. Legacy builds are not supported, in any way by Schrodinger: we simply provide them as a convenience for our users.