You're suggesting that the same guy, who told his own kids "no you can't have an iPhone, iPod or iPad, you have to use a windows/zune/whatever device", and then after leaving Microsoft, bought a basketball team, and told them they could no longer use their existing Apple products, would have OK'd the release of a cross platform development tool...
Ballmer was CEO for over 14 years, during which very little of this happened. While some of this was obviously being worked on under him, I find it hard to buy the idea that Ballmer did all the work and Nadella just swooped in and took the credit.
They may have been under development during Ballmer's time, but it's hard to believe that they would've seen the light of day under Ballmer's leadership. And if Ballmer released any open sourced products, I get the feeling that there would be major strings attached. And it would have a switch and bait sort of feel to it. Kind of like Oracle with Java and other technologies from Sun.
The fact is, Nadella has made open source a lot more palatable from Microsoft.
