I don't see anything that says commercial applications are not allowed but I also don't see anything that says they are allowed.Can anyone find anything definitive?
Is Google App Engine permitted for Commercial Use?
google apps
The full Guidelines are here: http://code.google.com/appengine/program_policies.htmlFrom what I read you can use the App Engine for commercial purposes.  From what I read Google lets you use it for free to get a taste for what it can do.  There specific usage limit is An application on a free account can use up to 500MB of storage and up to 5 million page views a monthfound in http://code.google.com/appengine/docs/whatisgoogleappengine.html.So basically it is free for any use deemed as legal within their policies (no spam, porn, etc) up to the limit.  Once you go beyond that you will have to pay for your usage.