Hi Wei,
So, if you want to use GroovyServ for Scala to run as a script, I think it's possible. Please try to specify the Scala's main entry point as the above Clojure's example.
However, if you expects something to improve a compilation time of Scala by the similar approach as GroovyServ, it may be difficult.
GroovyServ shortens a start-up time of "JVM". But I think the slowness of a compilation of Scala would be caused not by starting up a JVM process but by just the compilation sequence itself. If so, GroovyServ won't be able to address the problem.
Unfortunately, it's written by Japanese and a little old (2010). You would understand the keywords and commands even though you couldn't understand Japanese ;-)
I don't know the latest Scala's condition about compilation or something because I'm not Scala user. But the article might be worth for you still.
Regards,
Yasuharu Nakano