Impressive...How do you collect the email email addresses? Do you just ask people for their addresses?

Yep. When the app launches the very first time I ask for their 1st name and email if they want to hear about deals/offers, new apps, etc.

They can cancel out easily and never see the form again. But when you have a free app that quite a few people download, email addresses start accumulating pretty quickly.

I also recently started to use mailing list in my blog. I thought a mailing list will be useful in iOS and Mac apps as well. So I started a project building a universal framework for both the iOS and Mac platforms, complete with UIs. It illustrates the concept of code sharing between iPhone, iPad, and Mac apps with just one codebase. The fact that you got 30,000 emails proves its viability. The project is at https://github.com/rayvinly/DevNewsletter

I was under the impression that this was a paid app. How does it generate so much revenue while still being free?

I signed up for future posts (extremely well-placed sign-up form by the way!), but I didn't see a description of in-app purchases or other revenue model as a topic for a future post, which is why I ask. I am also using Android.

Thank you for this post by the way. This is amazing and I'm excited to read your future posts!

Great questions. Revenue is where it's at!

Initially it was just a paid download for the text of the Bible.

With more research in the App Store though I realized audio Bibles were selling much more than I was.

So I outsourced the audio (mentioned in the post I think) and now the model is that users download the original app (with the text) for free, and then can buy the audio as an IAP.

This works great on multiple fronts: I collect more email address, I rank better in search because I get more downloads, and the audio sells better as an IAP than as a stand alone app.

Wow, you are incredibly ingenious! Thank you for responding!

:) You bet