To get started right away with TextMate 2, you can download a perfectly free binary build from here.
Or, click here for instructions on how to compile it.
The GPL sucks.
Allan Odgaard released TextMate under this horrible license, but wants any modifications given to him as "public domain" so he doesn't have to be burdened by the same restrictions the not-free-as-in-speech GPL provides. To which, I say:
Any modifications in this branch are released under the SAME GPL license.