All of them? It's unheard of at a AAA development level to sell an engine without full source access; CryENGINE, Unreal, iD Tech, and Gamebryo all offer full so

All of them? It's unheard of at a AAA development level to sell an engine without full source access; CryENGINE, Unreal, iD Tech, and Gamebryo all offer full source licenses, to name a few examples.