Sorry, no idea. You might have to talk to one of the developers.

Out of own curiosity: What are the advantages of hosting on App Engine specifically rather than a VPS or a dedicated server or other cloud servers like Amazon, etc.?

You save maintaining OS stuff and have an easier admin role. It's aimed at developer to make the apps more scalable and less depend from os parts. If you have a managed vps and don't have to scale to dimensions which a node hardware cannot handle, you won't need to switch that fast.

Take a look at en.wikipedia.org/wiki/Jelastic for a vendor, which works with local providers to offer a AppEngine for PHP and other languages.
To see what Google App Engine means for a PHP script take a look at this:
entwickler.de/webandphp/working-with-php...platform-125769.html


I am not sure if the Limesurvey Team will modify the software to run on GoogleAppEngine soon.

There are restrictions and some kind of adapting would have to be done, to run on GoogleAppEngine.
cloud.google.com/appengine/docs/php/