PROTIP : In order to download the same Forge version for the shell, that you have in JBoss Developper Studio, you can cheat with the URL given on the website, which is

and replace LATEST with the expected number, like 2.13.0.Final to be in synch with the version available in JBDS GA v8.0.2

This way, you will not get version issues by compiling your addon with a version different that the one used at runtime.