Galaincha can run in Mac, but not natively. Since Galaincha requires the .NET Framework and Microsoft Edge browser to run, you will need to run Windows in the Mac and run Galaincha on top of it.
This can be done by installing Parallels in the Mac.
If your Mac has an Intel processor and the Leopard Operating System, Boot Camp (built in) supports installing and running Windows directly.
If not, there is a free software called Virtual Box (from Sun) which can host Windows in a Mac.
Once you have Windows running on your Mac, installing and running Galaincha is straight forward.