Well, the 3D engine itself is either available if you search previous news items here, or at GP32news, or GP32Spain. If you're after the commercial one, though, you'll need to contact either ThunderZ or the guy who made it in the first place (I'm not sure which) about getting first a license, and then the code in the first place. But it is a 3D *engine* in C; to make something with it, you have to compile the code, so I suspect it isn't of a massive ammount of use except to developers...
Someone correct me if I'm wrong.