
I did the same thing in admin_forum_manager.php: added
$permission_handler =& xoops_getmodulehandler("permission", "newbb");
$permission_handler->createPermData("forum_access");
$permission_handler->createPermData("forum_view");
$permission_handler->createPermData("forum_post");
$permission_handler->createPermData("forum_reply");
$permission_handler->createPermData("forum_edit");
$permission_handler->createPermData("forum_delete");
$permission_handler->createPermData("forum_addpoll");
$permission_handler->createPermData("forum_vote");
$permission_handler->createPermData("forum_attach");
$permission_handler->createPermData("forum_noapprove");
$permission_handler->createPermData("forum_html");
$permission_handler->createPermData("forum_type");
$permission_handler->createPermData("forum_signature");
in line 231.
Now it works.
Thank you for the help