Ask HN: How should I open-source my iOS app?

My friend and I just released out first iPhone app, "Silent Shout" (http://itunes.apple.com/us/app/silent-shout/id439580131?mt=8&ls=1), and we want to open-source it. I've never open-sourced anything, and have never done much more than fork open-source projects and modify them for my own purposes, so I'm quite ignorant about the process of open-sourcing projects.

Our goal is to allow people to use the code and learn from it for any non-commercial purposes. We want to retain the right to earn money from the project (through future in-app purchases, or adding a price to the app for v2). I'd love for this to be a collaborative project, rather than something like Canabalt (https://github.com/ericjohnson/canabalt-ios) which seems like its simply a one-time code giveaway. Is there a license which fits our case, and aside from setting up a public git repo (which I'm in the process of doing, https://github.com/workwithnano/silent_shout), does HN have any other advice for us?