I am aware of Factor, although I believe that conceptually, FORTH can only work in small systems. In a larger system, you can afford yourself something like Haskell (or at least Lisp) and the extensibility and proximity to hardware of FORTH will diminish in value, while the disadvantages will remain. In other words, with a bigger machine, you can go with more abstract language (distancing from hardware but keeping the extensibility), because the compiler/interpreter can be made more powerful.

I also played with FORTH mostly in Minecraft Redpower 2 (but before that I also read Jones Forth, which is excellent), unfortunately, to prove my original point, people didn't like it and longed for BASIC.