I would be very intrigued if they do indeed support JSP, or tomcat, or whatever (as you may be able to tell, I'm not experienced with JSP), but I put together a test page
http://whatariot.x10hosting.com/JSP_trial.jsp that I think should just echo out "Hello World", that just displays as all text in FF, so my guess is either it needs enabled for the individual account, or they don't support it. If you find out that it does need activated or something, please let me know.