On Linux you need mono, nuget and msbuild. I used a recent versions from https://www.mono-project.com/

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.