You might very well be right that the overlap's small, but note that AppJet is potentially for programmers who do have knowledge about deployment/hosting issues. How so? Well, such a programmer might not want to deal with hosting issues for a particular project. If the project s/he is attempting really is 100 LOC, then getting the app all nice and hosted and scaleable might take an order of magnitude longer than the actual coding does. AppJet, if it delivers nicely, could be a real win here.
"Hosting issues", although I am not entirely sure what are you referring to, become issues only when a certain level of complexity is reached. By the time you get there, you already implemented several appjets yourself.
I mean the term "hosting issues" to be pretty general -- implementing a data storage system (perhaps a database), caching, setting up server space, getting Apache to proxy to your app server, etc.
