Hi.

I would like to use an MFA authorization code that gives the user access to the forum in other applications associated with the user's forum data - this is a game server.
Does anyone know how to use this?

It should be possible as long as you call the IPS class that handles it:

\IPS\MFA\MFAHandler::accessToArea( APP, AREA, URL, MEMBER_OBJECT );

You can use one of the existing areas (like the login screen) or create a custom app to support a custom MFA location.