Just released an update to phpBBHS the main addition has been the Ad Free Upgrade system has been added.
Ad Free Upgrade System Features:
-Can be a set number of days or unlimited ad free
-Payment view area in the phpBBS admin area
-Paypal Sandbox support for testing
-Adds an upgrade link in the bottom of the forum to access the upgrade
-Integrated with Paypal. Ad Free upgrades are added as soon as payment clears with paypal.