Starting from Identity Manager 12.6 SP5 and onward, CA has set the JBoss version to be 6.2/6.3 EAP, meaning a licensed solution for JBoss.
This is per the application support matrix.
This would require customers upgrading to have a licensed JBoss server in order to upgrade.
There is no way to upgrade on top of existing 5.1.x JBoss version.