http://redcareditor.com is an open source, cross platform clone of Textmate currently in development. It supports Textmate themes and bundles, and for the split pane guys in here: yes, it does that too.

Last time I checked (a few months ago) it was pretty slow and unstable, but I guess the project is worth watching if you're not on OS X.

http://www.sublimetext.com/ is a good editor for windows, though I think it differs from textmate in a few areas which I think is developed by one person as well

Good suggestion for Windows. One key feature for Sublime Text is the minimap and for those wanting that in TM, Julian Eberius developed a TM plugin - http://julianeberius.github.com/Textmate-Minimap/

The minimap plugin is cool looking, but it totally chokes on large files and I never really used it anyway. It also kind of bugs me that it's in a drawer instead of a pane (which is why I use Missing Drawer for the project pane http://code.google.com/p/textmate-missingdrawer/ )

Essentially, it is. I believe Allan hired a developer relatively recently to assist him to TextMate 2 and other things.