I disagree: The GPL allows those smaller software houses to use the id engine without giving away their game resources. After all, id doesn't give away Q3 just

I disagree: The GPL allows those smaller software houses to use the id engine without giving away their game resources. After all, id doesn't give away Q3 just because it gives away the Q3 engine. As the game resources are what the players mostly associate with the game, you can still make and sell your own game based on a GPL'd engine without the GPL really cutting into your profits.