Gmax was created to advertise 3dsmax and to give every 3d Artist a first look on the interface and tools of the Max tools. The industry really needs artist who know the standard creation tools like 3dsmax, Maya, Softimage aso..

Also it was done for serveral Games like Quake 3, Rtcw but only for non-commercial use. So if you want to use it in a commercial way, you have to buy a full license.

Best way is to start with Softimage Mod-Tool the standard license is around 500 €.