Although I love old-school languages like Forth, Smalltalk, and LISP, I find it weird to use Forth for a DSL. I looked into the example and it's not very readable, to be honest.
The syntax is terse and a bit difficult to parse if you're not familiar with forth, since I follow many of their naming conventions. This is mostly at the lowest levels of code, though; it is expected that you'll end up building your own convenience functions and syntax extensions along the way.