And it naturally leads to the question: what other games would be nice to have access to from the source code up. It opens a huge number of doors, everything from private servers to full-on rewrites of the game as a single-player experience. For knowledgable coders, it turns every single patch and design decision into something that can be modified by the players. The breadth of options is almost overwhelming.
Of course, Ryzom is a niche title with a strong emphasis on these kinds of innovations, so in a way it's to be expected. But it's the closest we've seen to a mainstream game going this route -- so what would you like to see? An older game that could benefit from the publicity? A newer game you feel could be improved? Or a sadly-cancelled game whose source code could be used as a resurrection?