AOI is pretty old now, I think. I remember looking at it a couple of years ago! It's been overtaken by Sketchup, OpenSCAD, FreeCAD, Blender, web-based ones like Tinkercad, and various other open source cad and drawing programs. We do our development in SolidWorks, which is more of a professional package. I think Rhino has a Mac version in beta, which you can get free, or at least it was up to a couple of months ago.
Ian
RepRapPro tech support
