OpSim is still under active development and no stable release has yet been released. In the future there will be releases for Windows, Linux and Mac OS.
To download OpSim, please select your platform and location from below. OpSim is Free & Open Source Software.
Windows 32bit (test release)
On SourceForge you can find the latest development status of OpSim. Or checkout the sources anonymously from SourceForge with:
svn co https://svn.code.sf.net/p/opsim/code/trunk opsim-code