I'm not sure about all this and how legal this is. Yes I know that it's extremely heavily customized but you are using a free script as a base which is http://chevereto.com/

It's licenced under the creative commons licence which means your not allow to profit or resell it. Now since you've modified it so much what I suggest you to do is add the copyright link to chevereto which was on it when you downloaded it and sell this as a whole site.

That would be like buying a heavily customized phpbb site and theme which is fine. Whatever about the legal aspects of a link I don't think it's fair for you to sell the script claiming it as your own.

EDIT: I wouldn't have posted this if it wasn't for the fact you listed everyone who modified the script and said it was ok to remove the link to the person who modified it