[x2495iiii]

If it's a text-editing file and your model is in .ase formet (not .ase.blend, just .ase), then you can open it up with any text-editing program, as .ase is a text file format.

I don't think there is a version of biturn for the Mac. If I were you, I'd use a virtual machine for windows, or try to use google to find a similar program for Mac.