Does anyone know if the Zultys Softphones work on MAC OS?

yes it does.

Unfortunately, no MXIE does not provide a soft phone for mac or Linux like the Windows version does. There are a great many 3rd party soft phones like x-lite/Bria from Counterpath or Apples own "telephone" application that work nicely with MXIE for mac.

I like Bria if you want more features... telephone is a great solution for something a bit simpler and stripped down.