The "Download Now" link directs you to the iTunes App Store, where you must continue the download process. You must have iTunes installed in order to open the link, and you must have an active iTunes account to download the application. This download may not be available in some countries.
From Jan Misker:
Moderate all your GNU Mailman maillists with just a few touches.This application is an interface to the Mailman administrator webpages. The app has been tested with the latest version of Mailman, but it is still possible that in some situations the parser can not correctly handle the webpages. In that case please contact the developer in order to get the application working in all cases.Usage instructions:After entering the list email address the base url should be automatically filled in. The base url is the url for tending to administrative request, e.g. for a list with address email@example.com the base url will likely be: http://example.com/mailman/admindb/test_example.com Bug:Unfortunately there is a minor bug preventing you from entering a url in the base url field. It should be filled in automatically after you enter an email address, otherwise you can copy-paste it from another source. Of course this bug will be fixed asap.