No, you can hide this information, there's an option on design->look and fell
But if you change the kernel you need to release your changes as gpl. If you want to sell proprietary code based on eZ you'll need buy some of the proprietary license.
Welcome to the community portal. I'll keep it short, Thiago is spot on with his answer. You are allowed to hide/remove the copyright line / output to your site.
Regards Robin
Board member, eZ Publish Community Project Board - Member of the share.ez.no team - Key values: Openness and Innovation.
