I searched through the issues and there seems to be none on the topic that React is not truly open source, and how this might very well become a problem for every one using WordPress if Gutenberg is merged into the main product.

Here's some links for reference.

VMware disallowed usage of it after their legal department looked at the licence:
https://discuss.reactjs.org/t/legal-department-did-not-allow-use-of-react/3309/5

Another lawyer evaluating the licence:
https://www.elcaminolegal.com/single-post/2016/10/04/Facebook-Reactjs-License

Apache recently banning use of React due to this licence:
https://www.theregister.co.uk/2017/07/17/apache_says_no_to_facebook_code_libraries/

/.../ BSD-plus-Patents license includes provisions that mean if you, directly or indirectly, accuse Facebook of patent infringement, you lose the right to use and distribute Facebook's code.

Facebook are currently considering re-licensing React (and many others)

See facebook/react#10191

Also see discussions on make/core https://make.wordpress.org/core/tag/javascript/

Looks like Facebook are not budging - https://code.facebook.com/posts/112130496157735/explaining-react-s-license/