try to create a limited domain

app/Http/Actions/CreateAccount.php

@@ -92,7 +92,7 @@ class CreateAccount extends AddonController
         $productManager->loadById($params['pid']);
         $acc_limit = $productManager->get('acc_limit');
         $accounts = $productManager->get('acc_base') + $params['configoptions']['acc_add'] + $params['configoptions']['acc_new'];
-        if ($acc_limit >= 0) {
+        if ($acc_limit > 0) {
             $attr['userMaxCountCheckbox'] = TRUE;
             if ($accounts > $acc_limit) {
                 $accounts = $acc_limit;