Apparently it’s not even Nintendo, but trolls. Just that this is such a Nintendo thing to do that GMod doesn’t want to even risk it
EDIT: So the domain is owned by MarkMonitor, a service that monitors for copyright infringement and sends DMCAs. Nintendo HAS used them before. So that clears up any confusion there
Hope this results in Firefox changing it to be opt in and not result in Firefox going the way of the dodo - We can’t have Chromium be the only option, and without somebody developing base Firefox, the forks are going to die off