It's not a native app either, it's a web app that doesn't have standard controls. They could design it however they wanted as long as they could build it in HTML.
That being said, the Google Buzz app is just using the same UI library that Google has developed for all their other mobile offers (Gmail, Calendar, GTalk, etc.).
I think you have two things:
1. Google developed their library of UI elements that looks a lot like the iPhone ones.
2. Using that library, they made a new interface for Buzz. It does look very similar to Brightkite's, but only the location part can be really argued as "inspired", the rest is pretty standard indeed.
