After some time of decompilation using multiple decompilers, I managed to extract a working source code for asda2 server (original files found at:

).
Note that there
might be some issues with some server functionalities due to the decompilation process although the code compiles and runs.
You may download the source code from the attachments or github:

or from:
Use Visual studio 2017 to compile the code (.Net Framework 4 is required).
Have fun creating your unique server.
virus total scan link: