OpenCOR can be used on the following versions of Windows, Linux and OS X. Alternatively, you could try building OpenCOR yourself.
OpenCOR is supported on Windows 7 (32-bit and 64-bit) and Windows 8 (32-bit and 64-bit), but it should also work on Windows XP and Windows Vista.
OpenCOR is supported on Ubuntu 12.04 LTS (Precise Pangolin; 32-bit and 64-bit) and 12.10 (Quantal Quetzal; 32-bit and 64-bit), but it might also work with some other versions of Ubuntu and some other Linux distributions, though additional system libraries might be needed for the latter.
OpenCOR is supported on OS X 10.8 (Mountain Lion).