Here it is: https://iddevnet.dhewm3.org/
It's mostly complete (all articles are there), but a few downloads and several images are missing.
The Quake4 part may look like a Wiki but it's static pages, so search won't work.
https://github.com/dhewm/iddevnet#missing-files-not-available-on-archiveorg-either has a list of missing files, if you have any of them please post them here so I can add them :)
Have fun!
Didn't even realize it was down, thanks!
I checked the whois and it's still registered until October this year, I wonder why it's down. I don't se that site costing anything to keep up (it could be a free wordpress site it's that simple) except the domain name registration, unless MS took down the server it was hosted on.
EDIT: is there a way to archive the Doom 3 & Q4 sections in to separate PDF's so they can be shared on the internet?
http://iddevnet.com just redirects to bethesda.com
https://iddevnet.dhewm3.org/ has a link to a .zip for offline viewing.
It's no PDFs, but html that you can browse locally and share
Luckily someone with backups of the Quake4 articles with missing images turned up and they also had the missing animations.zip!
Now it's almost complete, only two (unimportant) images for Q4 articles and one for Doom3 are still missing.