As I understand it, changing the licensing will do nothing to affect the fork Microsoft already made. It might affect the next megacorp from doing the same thing in the future, but Microsoft can keep working on their fork without giving it a second thought.

This is for sure a cautionary tale for every open source contributor. Choose the original open source license very carefully.

Edit: Might I suggest that when picking the original license, you try to imagine how you might feel if the company that you hate the most (could be Microsoft, Google, Amazon, or other) does the most extreme thing allowed by the license.