I believe smrtinsert is referring to places that you could work at to write those languages, not that the languages themselves are impossible to find. I don't know if anyone is actually being paid by someone else to write ScalaJS, GHCHS and/or Js_of_ocaml.
Scala.js[0], GHCJS[1], and Js_of_ocaml[2] among others.
[0] http://www.scala-js.org/
[1] https://github.com/ghcjs/ghcjs
[2] http://ocsigen.org/js_of_ocaml/