The username and password is needed to manage your cloud account; a backend server that is used for build services and to manage the wireless test and debug fea

The username and password is needed to manage your cloud account; a backend server that is used for build services and to manage the wireless test and debug features. If you are not connected to the Internet when you start the XDK it will still function, but you will, obviously, not be able to use those features that require access to the cloud services to function.