Great! When are you going to start working on it?

Without the individuals willing to put in the work then directions like this are pointless, however well intentioned. Since no-one attached to the development of Textmate has expressed any interest in porting over to Linux, or any other platform, I find it unlikely that the situation will change in the near future.

It would probably be easier to write a new editor (in a different language) from scratch with a compatibility layer for TextMate bundles.

Or bring the GNUstep framework on par with Cocoa. Would be many years of work in either case.

I don't see the need to port TextMate to Linux. We already have Vim/Emac/Gedit.