So, after emailing the tech support team, this was what I got:
Well the form code itself is very very basic. It was based off of a
popular formmail script that was freely available. It is something
similar to this:
I'm not sure what parts would be beneficial to kind of ajax out, unless
the form just submits and immediately lets you know you're in the list or
something like that. What I've experienced is that you can always find
something that you can ajax to make it smoother. So I'd say it's
possible. Check out that formmail script above and see if you can figure
something out though.
Now, I tinkered around trying to get an asynchronous request going through Prototype, but so far, it seems non-responsive. The script does, indeed, use custom addresses for the different responses, so I'm wondering if these responses can be interpreted by prototype (maybe with a little help?) and fed back to update a div.
Unfortunately, this is as far as my skill takes me. I'm no programmer, so if someone else could take this on, by all means, please keep us updated here. We may even figure something out and add it to the wiki?