« So what is limiting you from adapting the source code of Twinmotion to include all of its APIs directly inside Unreal Engine ? »
TM is built on Unreal, exactly like Fortnite or any other app that one can build with Unreal. To bring back a compiled app in the editor we need to work on a « reverse workflow « . This is a technical challenge: lots of data gets tossed always when an app is cooked with Unreal, data that you would expect to see in the Unreal Editor.
Nothing limits us on the legal side, it’s just a ton of work to be able to do this successfully.