He is the founder and CEO of Barnes and Noble. Conservative estimates of his net worth puts him at 900 million dollars. He doesn't need the money. He also has rock solid confidence in the management team at GameStop since he hand picked them for their jobs there. This is nothing but his regular intervals of selling blocks of stock. He's done the same thing at B&N and that stock has split numerous times in spite of his sales of stocks.
This stock will double in value just on European expansion plans alone in the next 12 months.