Co-founder Dalton Caldwell:
In May of 2014, App.net entered maintenance mode. At that time we made the difficult decision to put App.net into autopilot mode in an effort to preserve funds and to give it ample time to bake. Since then every dollar App.net has charged has gone towards paying for the hosting and services needed to keep the site running. Unfortunately, revenue has consistently diminished over the past 2+ years, and we have been unable to return the service to active development.
We will be shutting down the App.net service on March 14, 2017. We are immediately turning off new signups and any pending subscription renewals. We are also going to open-source the code behind App.net on our GitHub page. You will have until the shutdown date to export your data. At that time, all user data will be deleted.
From what I can see, the service has been dead for awhile. This signs the death certificate.