This Depends if its a "Ready to Publish" Product or a "Custom product"

There is no restrictions for custom products, since you are creating a unique design, you can sell anywhere you like, and come back to the EA app to place "manual orders" so we can draw and fulfill the order.

However, Ecomartists retailers are should be cautious to sell "Ready to Publish" products on third-party marketplaces, because of duplicate issue from other Ecomartists users doing the same. This includes marketplaces such as the following:

There are no restrictions for: