I am a freelance programmer. I am going to develop a mobile multiplayer application (not a game). The front-end of the application will be implemented using Unreal Engine 4, and the back-end of the server side in PHP. Question: The mobile application and server part will be pre-sold for $ 1000, so I will need to pay a royalty?
Yes, you will owe royalties on revenue generated in connection with your product. Please note, however, the royalty exclusions in Section 5 of the EULA (e.g., no royalties owed on first $1M of revenue, no royalties for custom work-for-hire products).