We have been researching if Clojure needs JRebel support at all since most of the development there is done by composing functions in REPL. And for that case JRebel didn't seem to be required. But there was a case, when a class is compiled using class-gen macro - then the special integration with JRebel was required.
http://blog.robert-campbell.com/post/2760935713
Groovy is supported in JRebel officially.
Most likely, in the upcoming releases, we will add support for JRuby also. Actually JRebel is already capable and works with JRuby but it just needs some polishing.