Installation file is freely downloadable: BloodyMary-beta.ZIP (<1MB) (just download the zip file, extract and run setup.exe).
This simulator runs on Microsoft .NET Framework. If you don't have the platform installed, the simulator installer will help you to download it.
If you install the SimPlayer utility, you can run the on-line version here.
Some basic facts about problems with modelling of physiological systems that are in the background can be found in the section Modelling of the Exchange of Blood Gases (en/cs).