Skype for Asterisk is far from a third party hack. It was designed around the Skype Engine API, at a time when Skype was not providing access to that API to the general public (I think they still aren't providing that level of access). In fact, Skype approached Mark Spencer (original programmer of Asterisk), not the other way around. So while the integration was largely written by Digium programmers, the Skype connector has always been a direct project of Skype's.
As far as Google's communication protocols are concerned, they use all freely and openly licensed protocols, and support for them has long been integrated in Asterisk. (Yes, you can use Google Voice with Asterisk.)
Your comparison fails.