Good morning, Cerebrus. I've found a temporary solution for you, as per
http://www.php.net/manual/en/function.eregi.phpGo into your Sources folder and grab Register.php.
We're going to be focussing on Lines 198 and 199 (Search for "!eregi").
Currently, it's as follows:
Quoteif (!eregi("^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,3})$", $member['email']))
fatal_error("$member[user] $txt[500]");
You may want to try to change the {2,3} to {2,4} to see if that helps. If not (since it could very well restrict .museum domains), then you may want to take a peek at
http://www.php.net/manual/en/function.eregi.php.I'll be sure to let the Devel team know about this thread, though.