You mean one of Google's domains?

  # whois appspot.com
  [Querying whois.verisign-grs.com]
  [Redirected to whois.markmonitor.com]
  [Querying whois.markmonitor.com]
  [whois.markmonitor.com]
  Domain Name: appspot.com
  Registry Domain ID: 145702338_DOMAIN_COM-VRSN
  Registrar WHOIS Server: whois.markmonitor.com
  Registrar URL: http://www.markmonitor.com
  Updated Date: 2022-02-06T09:29:56+0000
  Creation Date: 2005-03-10T02:27:55+0000
  Registrar Registration Expiration Date: 2023-03-10T00:00:00+0000
  Registrar: MarkMonitor, Inc.
  Registrar IANA ID: 292
  Registrar Abuse Contact Email: abusecomplaints@markmonitor.com
  Registrar Abuse Contact Phone: +1.2086851750
  Domain Status: clientUpdateProhibited (https://www.icann.org/epp#clientUpdateProhibited)
  Domain Status: clientTransferProhibited (https://www.icann.org/epp#clientTransferProhibited)
  Domain Status: clientDeleteProhibited (https://www.icann.org/epp#clientDeleteProhibited)
  Domain Status: serverUpdateProhibited (https://www.icann.org/epp#serverUpdateProhibited)
  Domain Status: serverTransferProhibited (https://www.icann.org/epp#serverTransferProhibited)
  Domain Status: serverDeleteProhibited (https://www.icann.org/epp#serverDeleteProhibited)
  Registrant Organization: Google LLC
  Registrant State/Province: CA
  Registrant Country: US
  Registrant Email: Select Request Email Form at https://domains.markmonitor.com/whois/appspot.com
  Admin Organization: Google LLC
  Admin State/Province: CA
  Admin Country: US
  Admin Email: Select Request Email Form at https://domains.markmonitor.com/whois/appspot.com
  Tech Organization: Google LLC
  Tech State/Province: CA
  Tech Country: US
  Tech Email: Select Request Email Form at https://domains.markmonitor.com/whois/appspot.com
  Name Server: ns4.google.com
  Name Server: ns3.google.com
  Name Server: ns2.google.com
  Name Server: ns1.google.com

While appspot.com is a Google domain, anyone can register domains under it. It would be similarly surprising to see an official GitHub blog post under someproject.github.io

You mean like: https://say-can.github.io/

This is common in the research PA. People don't want to deal with broccoli man [1].

[1] https://www.youtube.com/watch?v=3t6L-FlfeaI

Looking at that link, I don't think that is a GitHub publication? It is marked Robotics at Google and Everyday Robotics.

My bad, it's a google-specific problem.

Fun fact: appspot.com was the second "private" suffix to be added to the Public Suffix List, after operaunite.com: https://bugzilla.mozilla.org/show_bug.cgi?id=593818

This is quite suspicious considering that google AI research has an official blog[1], and this is not mentioned at all there. It seems quite possible that this is an elaborate prank.

1: https://ai.googleblog.com/

I'n not certain but I think it's prelease. The paper says the site should be at https://imagen.research.google/ but that host doesn't respond

appspot.com is the domain that hosts all App Engine apps (at least those that don't use a custom domain). It's kind of like Heroku and has been around for at least a decade.

https://cloud.google.com/appengine

Spring 2008: 14 years!

Whoa, I feel super old, I first used it in 2011 when I thought it was new.

Not just that ... Google Sheets must be the all-time worst way to distribute 200 short strings.

IIRC appspot.com is used by App Engine, one of the earliest SaaS platforms provided by Google.