This is a free to use Drawpile server.
To host a session here, select the Remote option
in the Host dialog and enter drawpile.wolvan.at in the text box.
This server is hosted by Wolvan, if things don't work, take it up with him. The server also comes with limited capacity, so please be considerate and don't monopolize all of the resources.
Sessions hosted (or just listed) here should abide by whatever rules are set by the creator of the session.