How can you give up rights on an MIT licensed piece of software?
Permission is hereby granted, ...
If you created a fork and changed the license, then maybe, but what part of "without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software" would allow MS to direct the development of Qora or control the blockchain?
Even if they/you changed the license, people would still be free to run the versions which are MIT licensed.
It might take a lawyer of someone experienced in intellectual property rights to say for sure. But here is what I suspect: Qora devs sign the Azure contract. After several months of development under the Azure veil, MS can claim that the "new" Qora is significantly different from the "old" Qora, which was MIT licensed. And as such, they now have legal dominion over the "new" Qora.
If a company takes something that exists in the wild, something very common, and enhances it with some new design that significantly improves on the old design, then they can apply for protection (a copyright or patent) for their
enhancements to the original, public design.
I admit that I am not an expert in these matters. I am simply trying to contribute a healthy dose of suspicion to this opportunity.