Presumably it's a "single-page web app", where the HTML page is essentially empty except for JavaScript.

This JavaScript then performs the rendering by dynamically constructing an HTML page with the DOM, as well as fetching data from the back end, and so on.

It's a fairly common application model these days.

They probably use PhoneGap or something similar to glue into the mobile OS environment. (Edit: They use Titanium.)

My company is developing a very similar events app, also written entirely in JS (PhoneGap, Backbone, etc.). There are so many challenges in making it a smooth user experience comparable to a native app, but we've finally gotten there.

They are using Appcelerator Titanium, which is a cross platform app SDK.

You write your code in Javascript, and Titanium actually generates native code that is then compiled into an app.

This is the only reason I clicked here. I too would love to hear more on that aspect.