Wandering on the net, I found a website sharing some nice resources, by ShrimpWork.
Unreal Package Lib (https://shrimpworks.za.net/projects/unreal-package-lib/)
QuoteA small Java library for efficiently reading Unreal Engine packages.
Unreal Archive (https://shrimpworks.za.net/projects/unreal-archive/)
QuoteA persistent archive of user-created Unreal and Unreal Tournament content.
There's more to this work, and it could be usefull to look at the github links.
There's a
MQTT Client implementation written in UnrealScript, and new gametypes - perhaps usefull to see how implemented, idk.
EDIT. :
I want to add another link I found, not the same source. No need for another thread but it 's worth registering it, probably.
Event Grid for UnrealScript (UT2004) to make loosely coupled code (https://github.com/tderoos95/EventGrid)