The client is in version 9.1.5. This version is the one that Official WoW is currently using but we planned to release the content progressively, and in order: the 9.0 version first!

As far as add-ons are concerned, you have to take for the 9.1.5 version and make the updates as long as the 9.2 version is not released although the content is in 9.0.1.