The popup has an HTML form with a submit button. When clicked, some JS (on a separate JS file) does some AJAX. The click event is binded with jQuery.
The is exactly what's not happening i "External Load" mode.
Unfortunately I can't provide a link to the site that has the issue because it's on a development site.
I can provide a link to the production site, on which the popup is running on "Page Footer" mode.
http://www.ravellosystems.com/blog/using-red-hat-satellite-bootstrap-environments-ravello-aws-ec2/
The code running the AJAX code for the submit can be found in ravello.js (look for it in the page source, it's in the head).