TextMate creator Allan Odgaard has posted the code for TextMate 2 on GitHub.
I've always wanted to allow end-users to tinker with their environment, my ability to do this is what got me excited about programming in the first place, and it is why I created the bundles concept, but there are limits to how much a bundle can do, and with the still growing user base, I think the best move forward is to open source the program.
TextMate 2 is out in alpha and as a TextMate 1 user that would like to upgrade to a stable 2.0 version, I am skeptical that this is a good move in that direction.