(I am not on the App Engine team, but researched it recently to give a talk about it)

If the request is going through a static handler (as declared in app.yaml), then the request won't go to the Apps frontend servers at all, it will go to the static file servers. So, no, the app unloading shouldn't be relevant for static files.

I made this diagram for a recent talk that somewhat shows that: http://www.slideshare.net/wuzziwug/writing-apps-the-googley-...

EDIT: It looks like DryDrop may actually use script handlers, not static handlers, in the app.yaml, so app unloading would apply.