You would probably have to run it in a virtual machine. Something like this. http://www.vmware.com/products/fusion/
You'd still need a legal copy of windows.
I am in know way suggesting this will work properly, I've never used vmware. I know on a PC, MS Virtual PC 2007 will run FFVVII great on a virtual Windows XP install - XG midi and all (Software mode).
Also, on most new macs you can dual boot to some version of windows if you have a legal copy of windows. I'd try this.
If you've got an old power PC your trying this on, you can *try* bochs http://bochs.sourceforge.net/
but in my experience it's only really usefull to help develop boot loaders and OSs. You'd probably not want to try this unless you are very familiar with PCs and how they work.
I wouldn't go out and buy any of this stuff just to try it, as quite often you will run into strange and sometimes insurmountable problems running 3d apps in virtual instances.
It is unlikely you'd be able to make a windows app run native in Mac OS, especially a D3D App. I won't say it's impossible, but i don't think it will happen.