The technology itself was created by Autodesk, but the way you import into UE4 (the interface, the converter that occurs behind the scenes to make the engine understand what to do with it, etc) was designed by EPIC. So long as you are not using EPIC’s import method, but instead create your own custom method as part of your game, you are ok.
Basically if you add into your game a custom way of importing models, that is your own method, and does not use the engine import functions designed by EPIC, that is allowed. To do you will need to create your own importer interface, and tell your game how to use to import models. It is a somewhat complex thing to do on your own, but it bypasses the need to use the UE4 editor to convert and create custom meshes within your game.
I am not sure if anyone here has created a system like before for UE4 (larger teams may have) so it might be a tough road to follow, but if you are creating your own map editor as well, it would be worth it for your users if you don’t wan’t them to go down the individual licence path.
*EDIT: Well look at what I just found… have a read through , it discusses using the Autodesk FBX SDK:
https://forums.unrealengine./showthread.php?2605-Tutorial-Generating-custom-static-meshes-at-Editor-run-time
is not the answer fully, but could give you some ideas on how to go about doing . Just make sure it doesn’t use epics tools. 
Also Adding a link to the Autodesk FBX SDK for anyone wanting to read more about it:
http://docs.autodesk./FBX/2014/ENU/FBX-SDK-Documentation/index.html?url=files/legal-notice.htm,topicNumber=d30e116