The WordPress for iPhone source can be downloaded from subversion. This page has the instructions.
I downloaded the latest trunk version. The app is using the Keychain Services API to store account information so that next time, when the app starts, it would automatically login to the blog. Apple has a sample program called GenericKeychain that uses the Keychain Services API.
I have not looked at the WordPress for iPhone source in detail. But one thing I noticed was that NSLog is used a lot for debugging purposes. To prevent those statements from being printed in the release version, I think it is better to do something like this.
