I now have a download link for Naum 4.2. It is 100% genuine - has been checked and confirmed. I can't post the link due to forum rules so if you want it PM me.
With Naum 4.2 you have to remember it loads as 1 core by default so you have to set it to the right number of cores when you load the engine. Maybe this is why some people have thought it weaker as they have been using it single core ?