This is what I was told a few months ago:
Yes the DE's are hosted on different server to the main sites, also the DE's already support HTML5/older this is how they work on iPhones etc which do not support Flash. At the moment the desktop version will look for Flash and default to this, we are planning to switch to HTML5 as the default with a fail back to Flash if needed as not all our customers have support for HTML5 on their devices. We would also need to remake the older DE's for them to work over HTML5 as default, but this going to be done early next year.
I've been looking at replacing the software we use to make the DE's for a while now but so far I've not found one that creates HTML5 versions reliably or better then the app we use at the moment.
Neil