Scott’s correct, Virtualmin doesn’t support Tomcat (though you could always set it up manually if you wanted, but Virtualmin doesn’t simplify that process).
You can enable Perl, Python, and Ruby handling in Virtualmin Pro or GPL, it’s just a matter of making sure that the correct Apache modules are installed, and that Apache is configured to process that particular scripting language… or you could make a .cgi script in the /cgi-bin/ directory.
There’s an Install Script for Python’s Django web framework available in Virtualmin Pro and GPL.
Virtualmin Pro has an additional feature, where it can run Ruby scripts using Mongrel, and will configure that for you.
adding support for turnkeylinux-based distros (appliances) could greatly simplify managing things like Java/Node.js or Ruby on Rails via Webmin/Virtualmin