The following subdirectories are collections of third-party packages used by Opus/UrbanSim. These are intended to be stable copies of supporting software used by the system. Generally, you can also download these from the official websites for each software component; but if the other website is down or has changed, this will serve as an alternative.
The subdirectories are for the different platforms we run on, or for source code that can be compiled for any platform. To keep things simple, the web page for each is produced using the "directory listing" capability, i.e. it is just a list of the files available.