erlang and scala, do they run on apache?
Scala is JVM based so it should run on Tomcat, though I haven't tried it, but, it won't run on a standalone Apache installation, as Apache doesn't run java.
I don't see how Apache can run Erlang, but if you wanted to run Erlang for a webserver app then you could use Yaws. You may find this comparison of Yaws and Apache interesting.
As James said, both the Erlang and Scala/JVM platforms don't have a way to run directly in Apache.
However, you can always use Apache's mod_proxy
to make another service appear to be in a subdirectory of your webserver (if you have port restrictions for JavaScript or whatever). Take a look at http://httpd.apache.org/docs/2.2/mod/mod%5Fproxy.html
Apache mod_proxy will allow you to "front" any web server/app with Apache. There is mod_jk for connecting with things like Tomcat (for scala). http://yarivsblog.com/articles/2007/01/11/erlyweb-tutorial-creating-a-simple-login-page/ shows how you might run erlang with its own web server. I don't believe there is a mod_erlang yet (not sure how that would actually work).