Last modified: 2014-02-12 23:54:00 UTC
The link points to a file (mobileRedirect.php) that lives on the WMF cluster but is not packaged with the extension. The functionality of mobileRedirect.php should be integrated with the extension and made useful for non-WMF use cases.
This is resolved as of r113865 - 'permanantly disable mobile frontend' was removed in favor of a simpler, persistent, and more intuitive desktop/mobile view toggling mechanism.