I assume you are referring to the mc-oauth.net service? I see that domain is indeed expiring (Expired May 2022, still in pending delete status). Once it becomes available it could be grabbed by a bad actor and make any website using it vulnerable to account takeover, so I would recommend removing this extension from any forum that still uses it.
I see there's a mc-oauth.com on the internet, but I have no idea if it's the same service that migrated domain or another implementation of a similar concept.
I'm going to add the incompatible badge for now.
