It would be a pretty cool (but I'm sure huge) project if WordPress started an open source app building template, similar to the way WordPress is for building websites.
I don't know anything about the code, or even what kind of code it is, required to build apps. I've seen a few of what claim to be easy, do it yourself builders, but they look extremely generic and probably don't offer much as far as customization.
You would also have the advantage of being able in integrate them with existing WordPress sites.
Just an idea. I would love to see it happen.