If for any reason the Mac thread must be referenced, it can be found here:
viewtopic.php?f=27&t=2337&hilit=macbookTry to disable OS X Gatekeeper when you copy MM8BDM to the applications folder because OS X may recogonize 8BDM as a security hazard otherwise. Off the top of my head, I believe this is only applicable to OS X Mountain Lion and later.
If you're having problems with the OS X download after that, then there are various official Windows options your friend could consider. Is your friend's Windows emulator an official product? If you go with Windows, the options depend on how strong your friend's Mac is: you could either run Windows natively on the Mac or use a program to run what is basically an OS X application of Windows (it would be treated as a regular application such as Word, Excel, Powerpoint, etc.).