suggestion:
Running from within eclipse, the javac ant task with the option fork="false" fails compilation task. I've set to true so it uses the eclipse java runtime. This also applies to JForum2 code base.
Also, on the subject of compiling and deploying.
Tip to other developers. Create a Mavenized version of the project with the maven-archetype-webapp archetype. Quicker to work with than Ant and allows for runtime debugging in tomcat with the .m2-wtp plugin.
Until JForum3 is in a GA release... Best of to the developers of Jforum3