Anything from the marketplace can be used in other applications unless it is clearly stated in the product that its only for use with Unreal Engine. However, you should be careful not to use any Unreal Engine Starter Content of other assets from the engine, only use things you’ve purchased on the marketplace.
Hope this helps. (:
Edit: Here is a link to the Marketplace Knowledge Base where it speaks about marketplace content usage.
https://marketplacehelp.epicgames.com/s/?language=en_US