Update: You can now backup Gmail chat logs with Gmail Keeper, details here.
Google does not open Gmail chats API
We are constantly receiving requests from Gmail Keeper users for backing up Gmail chats history with Gmail Keeper, it seems that the chatting feature in Gmail (including Google Apps) is commonly being used, but unfortunately, since Google does not currently open the API (application programming interface) which allows downloading chats history from a Gmail account, it’s currently impossible to do that technically.
Gmail Keeper will backup Gmail chats in the future
The good news is, as soon as Gmail server opens an interface for accessing chats history to third party programs, we’ll follow up immediately, to add the Gmail chats backup function to Gmail Keeper, so ,eep an eye on Gmail Keeper 😉
Currently it can backup emails from all folders and labels from your Gmail account, and the labels are reserved in the local backup data, currently you can see the associated Gmail labels with modern zip archiver program (e.g. the free 7-zip), but in future versions will be able to view and search the local backup data with Gmail Keeper by using a Gmail-like interface.