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.?
I answer at the LimeSurvey forum in my spare time, I'm not a LimeSurvey GmbH employee.
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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.