I didn't know Komodo used XUL. I tinkered with XUL, a little, many years ago, but only enough to satisfy curiosity.

Pale Moon started as an alternate build of Fire Fox. Over the years, it became it's own browser, especially since FF started being dumbed-down. It's kept many of the features that were removed from FF. As I recall, the project plans to keep XUL as well as FF extension support, so maybe Komodo could switch over to Pale Moon.