Why is it dead. The Sparrow team won't work on it any more... but they weren't going to work on the Windows version anyway. If you were writing it, why not keep doing so?

Obviously you might have to change the artwork, since that belongs to google now. Otherwise, it sounds like this is just an email client that YOU wrote.

Why wouldn't you start with libetpan? It has been available for years, and it's well known Sparrow used it. This story smells fishier by the moment.