Running on 1.22alpha (09/2013) on Ubuntu 12.04 server.
As documentation is slightly lacking here's a couple of tidbits. To remove the SAFE, i.e., Password feature, make your statement as {{#iDisplay|URL|WIDTH|HEIGHT}}. Leave the SAFE out. To turn on password just include the |1}}.
If you are running your own wiki boxen, you will want to edit the file iDisplay.php in your /path/to/wiki/extensions/iDisplay/ directory. On or about line 60, change the URL to match your instance of iDisplay.
Works perfectly.