3
           
            
                
     
    
    The code is not in register.php, but in include/common.php from line 233:
 if ($xoopsConfig['closesite'] == 1) { 
        $allowed = false; 
        if (is_object($xoopsUser)) { 
            foreach ($xoopsUser->getGroups() as $group) { 
                if (in_array($group, $xoopsConfig['closesite_okgrp']) || XOOPS_GROUP_ADMIN == $group) { 
                    $allowed = true; 
                    break; 
                } 
            } 
        } elseif (!empty($_POST['xoops_login'])) { 
            include_once XOOPS_ROOT_PATH.'/include/checklogin.php'; 
            exit(); 
        } 
        if (!$allowed) { 
            include_once XOOPS_ROOT_PATH.'/class/template.php'; 
            $xoopsTpl = new XoopsTpl(); 
            $xoopsTpl->assign(array('sitename' => $xoopsConfig['sitename'], 'xoops_themecss' => xoops_getcss(), 'xoops_imageurl' => XOOPS_THEME_URL.'/'.$xoopsConfig['theme_set'].'/', 'lang_login' => _LOGIN, 'lang_username' => _USERNAME, 'lang_password' => _PASSWORD, 'lang_siteclosemsg' => $xoopsConfig['closesite_text'])); 
            $xoopsTpl->xoops_setCaching(1); 
            $xoopsTpl->display('db:system_siteclosed.html'); 
            exit(); 
        } 
        unset($allowed, $group); 
    } 
}  
You'll have to change that to check if the requested page is register.php (and the user is not logged in, perhaps) and if so, allow the page to be served.