in theory if someone or one person was to wright there own unreal-script and it was entirely there own work and only used the udk editor to rig up the own custom nodes and use there unreal-script to developed a game and didn’t use any of the coding to make the game run and only used custom coded node’s to make it would they still have to pay royalists to the udk development team?
If UDK (or UE4) is used to create a game, even under the circumstances you described, royalties are owed.