After weeks of searching for a platform that did everything I wanted and worked on appengine I have decided that maybe I should go ahead and create it myself. My intention with the forum was always to create a CMS at a later date and make the forum available as a module within that CMS.
This would have required alot of work at a later date because the best platform I could find for appengine was python and I wanted to do the CMS in Java. This would have required porting the forum to java, or at least a language running on Java at a later date. Not something I was looking forward to, so I have decided to create enough of the CMS to integrate the forum with it and take care of the templating and url routing for me that were annoying me with the servlet approach to website development with Java.
The initial work on the CMS is going to be based off my experience with DotNetNuke as I like the flexibility of DotNetNuke even if they underlying code leaves a little to be desired at times. Although I will be using a similar tabs/modules approach with the CMS the underlying workings will be quite different as I will be attempting to create a templating engine that is easy for designers to use by keeping to the MVC architecture and leaving all Java code out of the templates. This has an added advantage of keeping the template logic separate enough to allow for modules to be written in different languages without confusing things by having to Java for the views.
This whole process is proving to be quite a headache though as I try to figure out all the details for the CMS implementation and deciding what to build and when. I have never attempted a project even close to this size and complexity before so it will be quite the journey I am sure, and hopefully I will be much the wiser for the experience once this is all over.