Bubble's Terms of Service state the following: Sellers may only offer User Components on the Bubble Marketplace. Sellers may promote User Components on their own or third party sites, but any “purchase” link or the equivalent must direct the user to the Bubble Marketplace (and not via a frame or pop-up but via a re-direct).
If you believe a Seller is in violation of Bubble's Terms of Service, you may contact our Support team for further assistance.