Is it permissible for the owner of online courses and educational lessons to obligate students not to share them with others, or to sell them after purchasing them?

These courses and lectures have an intellectual property right that entitles their owner to retain their copyright and distribution rights, and they may not be published or distributed except with his permission. As for someone who buys a copy and owns it, he may dispose of it by selling it, gifting it, or through other lawful transactions. This does not constitute an infringement of the author's rights, unless he prints other copies from it to sell.