[trhway]

It isn't about Ballmer vs. Nadella. It is about the scale and importance of Azure and Linux/OSS usage there that made the MS hugely vulnerable to the same style patent attack that MS has been doing all these years against Android and the likes. Joining OIN they almost completely mitigate that risk. MS does that it has been always doing - milking and protecting its cash cow as much as possible.

[HankB99]

Can this move (WRT patents) be revoked if MS decides that it is not in their best interest to share freely?

At present it looks like they really have changed. Could they change again?