It's possible to install Wine on Mac easily: just look for a software named WineBottler (or its rival Wineskin).
Its installation package includes Wine, already packaged as a standard MacOSX application.
It is therefore possible to install WineBottler (with its Wine.app) (or Wineskin) and to run with it GIMP for Windows (http://gimp-win.sourceforge.net/
), which allows to run the Mathmap plugin and, yes, also the PSPI plugin on a Mac (PSPI and the last version of Mathmap do not exist in a native version for Mac).
Besides, it is possible to use on your Mac many .8bf filters (photoshop plug-ins for Windows) also by using (with Wine and WineBottler or Wineskin) some Windows freeware applications like Image Analyzer, PixBuilder Studio, Chasys Draw IES and IrfanView (it is advisable to try them all, not only IrfanView, and, if needed, to read the information on their sites about how to use the .8bf filters with each of them).