@aardrian Hi Adrian, the domain expired a month and a day ago.
When prompted last May, we resolved to let it expire because 1) we recalled it was not meant to be indefinite and 2) when the webat25.org website was migrated to W3C servers in Feb 2017 we installed a permanent redirect to https://www.w3.org/webat25/ and we felt safe letting the domain expire as it would have been redirected for 17 months.
@koalie Fair choice. I found out because the 404 spider on my site let me know. At least now I know I can update the link to W3C instead of Wayback. Though it does make me a bit sad.