I think you guys make fair points, although I would mention about the point about "concept" in particular: You are by no means required to accept anyone else's conceptual alterations, or even to pay them any mind. What "Freeing" your software means literally, is that it can outlive your vision, your personal interest, and perhaps your very life.
Well, if all that comes of this in the end is that you guys end up properly licensing and releasing the source of software you're no longer interested in maintaining, then I guess we have made some progress.
Originally Posted by Mrs Beanbag
Of course it is possible to open-source a game engine but not open-source the actual games.
I posted a Wikipedia link to an enormous number of games -- not engines -- that are open.