How is the tongbu tui app able to be installed directly from the browser on non-jailbroken iOS devices?
All a person need to do is take a regular iOS device and visit http://tui.tongbu.com/m/iphone.html and click the big grey button with the apple logo, and then click install. Then the tui app will be installed. How are they able to distribute this app on non-jailbroken devices without the app store? And how can this be replicated?
Answer
1) They may signed it with enterprise distribution key and in such case they are violating Apple agreement. Otherwise, they have an app on AppStore and they downloaded IPA through iTunes and put on their website.
As result, they have signed IPA (enterprise or appstore based) which will work on any non jailbroken device.
2) Second part is enterprise distribution mechanism. Generally speaking, what you do is your prepare enterprise distribution manifest (xml plist) which points to ipa files and other resources (as example icons). And you create a button with the link to this manifest. Link should look like that:
<a href="itms-services://?action=download-manifest&url=<URL to Manifest>">Some text here</a>
Couple of additional useful links regarding over the air distribution:
http://aaronparecki.com/articles/2011/01/21/1/how-to-distribute-your-ios-apps-over-the-air