As CoffeeScript also went through this same process, bootstrapping itself away from an original Ruby-based compiler (at this moment: https://github.com/jashkenas/coffee-script/commit/6446e0004c...), Kal is now in some sense "two self-hosted steps" away from a "normal" language. That's pretty neat.

GorillaScript (here: https://github.com/ckknight/gorillascript/tree/master/src), Coco (here: https://github.com/gkz/LiveScript/tree/master/src) et al, are also implemented in themselves. I hope that this trend of compile-to-JS languages tending to self-host continues.