Caiden, likely what is really going on is Udemy doesn't want member accounts or Udemy access/content resold outside of their partner/affiliate programs.
Using "copyright" as the reason is simply the path of least resistance when dealing with sites, including eBay, who are accustomed to processing DCMA takedown notices, to achieve that result.
https://www.udemy.com/terms/
"Udemy hereby grants You (as a User) a limited, non-exclusive, non-transferable license to access and use Submitted Content and Company Content, for which You have paid all required fees, solely for Your personal, non- commercial, educational purposes through the Services, in accordance with these Terms and any conditions or restrictions associated with particular Courses or Services. All other uses are expressly prohibited absent Our express written consent. You may not reproduce, redistribute, transmit, assign, sell, broadcast, rent, share, lend, modify, adapt, edit, create derivative works of, license, or otherwise transfer or use any Submitted Content or Company Content unless We give You explicit permission to do so. Submitted Content and Company Content is licensed, and not sold, to You."
"You may not transfer Your Account to any other person and You may not use anyone else's Account at any time. "
