Is it possible to use mod_jk as reverse proxy without installing Tomcat? I have Apache and JBoss installed, I don't see why I should install Tomcat? Thanks.
mod_jk just speaks a particular protocol (AJP13 to be specific). It's not bound to Tomcat in any way. Sure, you can use it with other products.
Spoiler alert: JBoss uses Tomcat as it's servlet container internally.