Topic on Talk:Return to Castle Wolfenstein
Using the GOG version, I was able to retrieve a list of servers without any modifications. While iortcw is installed, I renamed my autoexec.cfg and used the original WolfMP.exe. Most, if not all servers are however running version 1.42b, that I could see.
It seems likely that the mod in question is no longer required, however, I do not know the details around it. Its GitHub page looks more like an archive, dating back to 2018, while it seems the master server got back up around 2016. I do not know the history here.