The extension does not work if read access for anyone is disabled and only enabled for logged in users ($wgGroupPermissions['*']['read'] = false;).
If a user with read permissions logs in then a page about permission problems is shown: "You do not have permission to read this page, for the following reason: The action you have requested is limited to users in the group: Users."
After switching off the extension and without any other changes the wiki appears normal.
Tested on MW 1.27.1.