It can be made the argument that the mod is a way to circumvent copy protection and due to this in conflict with the DMCA (and all the equal laws in many other lands).
A mod like this is not the worth to go to court over, so it is only understandable that the creator has pulled it from the net the best he could. And even if Nexus had pulled the mod down over a DMCA notice nobody should blame them. We may not like the laws but Nexus Mods is bound to it.