TechCrunch reports that Yahoo have released a tool called BBAuth, which allows third-party applications to access Yahoo’s sign in services and will allow third-party apps to gain access to Yahoo user’s data (with prior permission, of course).

This opens Yahoo’s API (read more on APIs here) so that you can login with the user’s Yahoo credentials and access, say, a user’s Yahoo photo information from another application.

This is a big step. Most of the heavyweight login services - MSN/Windows Live, Google etc. - don’t allow this kind of usage of their data and Yahoo are really singling themselves out.

With fierce competition from the likes of Google, but still with some very popular services under their belt such as Flickr, Yahoo are obviously trying to get developers to extend the potential of the Yahoo sign in API and the Yahoo services.

If you do want to build an application (web or otherwise) that uses the API, you do need to get it officially approved by Yahoo in order to receive a secret key that gives you access.