I touched on this in the most recent devlog, but to catch up on this topic:
I’ve been following up with Epic for distribution of the Unturned 4.x Unreal Editor (which according to the Unreal EULA can only be made available through the Epic Games Launcher), so that should be on track for the first testable version. It will contain all of the Unturned project files and .uassets minus source files that can’t be redistributed e.g. audio.
4’s c++ code does not have any third party dependencies, so it shouldn’t be an issue to make that available as well. For example Unreal Tournament’s c++ source is available on GitHub.
Even without the c++ source download the majority of my code for 4 is exposed to blueprints, so modded gameplay features are possible purely from the downloaded editor.