Github appears to have disabled access to a number of repositories in response to a DMCA takedown by Whatsapp's general counsel in February 2014. These repositories appear to contain code that allows developers to create apps that can communicate with the official whatsapp client. The biggest target of this takedown is Tarek Galak's Open Whatsapp platform. http://openwhatsapp.org/
Take a look at the takedown notice here - https://github.com/github/dmca/blob/master/2014-02-12-WhatsApp.md