Hi, Andy,
Good to hear a friendly voice and know I'm not totally alone here!
Almost certainly not OSX compatible, although I'm no guru. It uses .NET framework, so in principle should run on any machine and any operating system that supports .NET, but in practice I think that means Windows.
Don't really know.
The up-side of using .NET is that the executables are tiny. Separately, the high degree of parallelization and use of C++ for the low level stuff means it's also blazing fast.
Best,
Mike