If is anybody here to answer to this question. Why is Unreal Engine 4 free but Unreal Engine 3 not. I know the answer but I want to see some opinions
This is my opinion:
UE3 contains middleware which can not be removed and there are licensing agreements between Epic and those other companies which prevent that. As well support for it while it is free, and support for UE4 at the same time would be very expensive.
UDK is an option for you if UE4 is not an option for your because of system requirements. It’s licensing is on the UDK pages. For licensing UE3 itself you will need to contact Epic directly.