You can have a maximum of two simultaneous activations at any one time. It can be installed on more than two computers but cannot be "active" and used used on more than two at the same time. It is possible to "move" activations between computers but this is best done via your Magix account, rather than the option within the program.
The software is Windows only so will work on a MAC only if you have Parallels, or similar, and a full version of Windows installed. Even then, success is far from guaranteed!