A Forth REPL on Voyager would be news to me. It's possible, because I do know that Forth was used to program some flight instruments on later missions [1] but even then it didn't include a REPL.

I don't know anything about what is happening in Haskell-land, but from your description it sounds like what they are doing is very similar. Haskell shares a lot of intellectual DNA with Lisp so it's not surprising that it would end up being used this way.

[1] https://flownet.com/gat/jpl-lisp.html, see the "Miscellaneous stories" section.