Depends on the project. I've seen the argument from game developers (e.g. dwarf fortress) that open sourcing the game takes a lot of effort. I wholeheartedly

Depends on the project. I've seen the argument from game developers (e.g. dwarf fortress) that open sourcing the game takes a lot of effort. I wholeheartedly disagree. You flip the switch, make sure there's an appropriate license, and the community can do whatever they like with it, and if it's well-known enough, they will. Native source ports for example. Which just happen to be the biggest reason I want the source to games. I don't know how much clean-up id did on doom's source before releasing it, but my understanding is that they didn't do that much. And I wouldn't be playing Doom today if it weren't for that source dump. I'm not playing dwarf fortress. I kinda would like to, though.