Even that requires significant effort that companies are not willing to invest. They'd have to scrub the server of proprietary code, like integration with an account server, and update the client to work with the new system.

I'm not in the game industry, so I may be wrong, but there doesn't seem to be any push in the game industry to use open source for common problems.

Why should a matchmaking/game browser use proprietary code? Create standards and use off the shelf components for common problems. Whenever I go into the settings menu of a game I wonder how much time has been spent reinventing it.