Our website provided a free download of aGPSS 1.30 for Mac. This software for Mac OS X is a product of Ingolf Ståhl. The program is included in Education Tools.
From the developer:
aGPSS is a modern version of GPSS. This application is a streamlined version of GPSS, a General Purpose Simulation System. The GUI with the block diagram facilitates learning and understanding. The programs are similar to real problems. The block diagram with 22 different graphical symbols is useful for modeling the problems. aGPSS allows for automatic animation with dynamic block statistics.
You may want to check out more Mac applications, such as eduMap, FRS Clocks and Time or Jers Flash Card Viewer, which might be related to aGPSS.
Teaching Tools