From @cubap on October 16, 2015 20:1
The current implementation of private uploads was meant to file a small gap while other options were brought online and brought with it a host of restrictions to prevent IPR issues. Rights become less of a concern by replacing the current module with one that will connect to remotely hosted images, at public institutions' repositories, hosting services like Flickr or Dropbox, and privately controlled image servers.
Copied from original issue: cubap/TPEN3#17