Yes, you are allowed to use our products in commercial projects, as long as you do not distribute the product’s source files. Since we exclusively sell our products on the Unreal Engine Marketplace, licensing conditions are to obtain from Epic Games directly. Should you see or receive our products from a place other than the UE Marketplace, you will have no permission to use the product(s) and ought to report the provider immediately, either to Epic Games or to us.
“Besides using [UE Marketplace products] for learning, experimenting, or prototyping, you may use Marketplace products in your own shipped products. However, you can’t sell or sublicense Marketplace content to other developers for use in their products, e.g. via website or ecommerce mechanism built into a 3D development tool.”
(Source: https://marketplacehelp.epicgames.com/)
For more information see the official UE Marketplace help website.