what this requires from developers: possibly documenting protocols in an open way when they choose to shut down games so that people can re-implement FOSS servers

“playable” is open to interpretation, and does not include trademarks, copyright, etc… nobody is asking for to allow assets to be traded (ie piracy), or open sourcing any code

but if you have purchased a game, and the servers for that game go away, someone else should be able to re-implement a method for allowing those games to continue being played

… also if DRM servers go away, you should disable the DRM somehow: you don’t get to just say that the DRM and therefor the game isn’t available any more