The problem is that their game is proprietary due to necessity to make profit. If Valve was a non-profit and made their game engine (Source 2?) free software, A

The problem is that their game is proprietary due to necessity to make profit. If Valve was a non-profit and made their game engine (Source 2?) free software, AMD would just send their patches into upstream, or, if Valve refused to accept them, they would fork the game, so AMD users could play with each other with less lag.