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YES, with a lot of missing features (parallel queues, cron jobs, mail, XMPP,..), some hidden security issues, poor performance and stability, it is technically possible.
As you probably guessed, it's a bad idea.
Take for example the HTTP server; using the development server you would put in Production an undocumented BaseHTTPServer, quite impossible to configure and with probably some hidden security flaws ready to be exploited.
As @Drew well said, there are better choices out there to run you Google App Engine code in a Production ready environment that is not GAE.