AS7 was missing the section where it set its default execution environment. It was therefore set to JavaSE-1.4 instead of 1.6. This means your version 5 JRE would be acceptable.
I've updated the critical issue for the creation of a new JBoss 7 Runtime... but you probably have to delete the current server and runtime and recreate
them from scratch. This was a big overlook on my part.
Adding in the ability to "choose" a jdk can be added, but maybe a bit later. For now I've fixed the critical issue, and the execution environment is now correct. Your version 5 jre / jdk should be ignored and not chosen now for launching as7.