Key to understanding is that GUI operations were two-handed, descending directly from NLS (people have all seen the ‘mother of all demos’², right?). Right hand on the mouse, left hand on the left function key cluster³ — one of the Star papers is explicit that the left cluster was a direct substitution for the NLS/Alto chord set.
A very noticeable difference from the familiar Lisa lineage is Move and Copy vs Cut and Paste — there was no clipboard. (Here I think Star got it right and Tesler got it wrong: the condition of the clipboard containing invisible fragile state is a mode, and a worse one than move-in-progress.)
¹ https://github.com/livingcomputermuseum/Darkstar
Then you should be able to do:
git clone https://github.com/livingcomputermuseum/Darkstar.git
cd Darkstark
nuget restore
msbuild
This should produce a Darkstar.exe below D/bin, which you can execute using "mono Darkstar.exe".On Windows, if you have Visual Studio, then you can just open D.sln and build the project.