It's possible those files are completely different in free & paid verisions, did you add moderatecontent.php in /app/vendor/moderatecontent/ I would start again if I where you, are the database entries still there?
One question: If I update to 3.16.0 now, will it work despite the files modifications, or I need to just delete the added ModerateContent tables and to update my Chevereto instance?