The understanding I've gotten from statements in the past was there was a fear of loss of intelectual control of the systems. So you don't see people doing anything like has been done for Panzerblitz, Panzer Leader, Arab Israeli Wars, Assault or World at War to name just a couple of other platoon scale games on Vassal and hugely supported on the web. If I'm wrong point me to the site like Imaginative Strategist or myassaultpage.