Took some time for dummie like me to figure it out, but if anyone else needs to do it, then in classes/address.php remove "'required' => true" on this line (or where neccessary):
'address1' => array('type' => self::TYPE_STRING, 'validate' => 'isAddress', 'required' => true, 'size' => 128),
and then modify on theme folder files address.tpl and authentication.tpl (make address1 similar to address2).