I think it was way overdue.Should settle the major concerns most react developers had.
I personally didn't have an issue with the BSD+Patents license--I think it's fine that they wanted to deal with patent trolls more easily. If you actually ended up in court against Facebook, you'd be in a better spot using React and it doesn't mean that you'd have to rewrite your whole app. There's an article from a patent attorney that explained some great points. I also talked about this on my podcast.
Having said that, other open source projects like WordPress were forced to move away from React due to not wanting to force their users to agree to the same license. I understand that there's still some fear that prevents people from using React. The MIT license switch makes it where practically anyone can now use React unless they just don't like the library. Which is a huge win for Facebook and the React community.
Don't see any negatives with the licence shift at all, at least for us consumers. It's one less obstacle and I'm sure more companies will allowing their engineers to incorporate it into their UIs. Whilst other options exist already, my feeling (and of other engineers I've spoken to about it) is that nothing out there is React, except React.
Now let's just hope it stays this way!
This is great news for the OSS community. More importantly the news that GraphQL changing licenses is very welcoming: details here
Not much more that i can say to be honest, things like this are simply good news.