Which one has more value? A file included in the repo, written in legalese, on which Every single source code file's copyright headers point to (and the README file as well), or an ambigous blog post?

Reading the file in its current form (https://github.com/facebook/react/blob/b8ba8c83f318b84e42933...), You lose the license to make, have made, use, sell, offer to sell, import, and otherwise transfer the [React] Software.

You lose the license granted in the PATENTS file, but you might not lose the license granted in the LICENSE file. (IANAL, so no idea whether that's true.)

Does the additional patent grant in the Facebook BSD+Patents license terminate if I create a competing product?

No.

Does the additional patent grant in the Facebook BSD+Patents license terminate if I sue Facebook for something other than patent infringement?

No.

Does the additional patent grant in the Facebook BSD+Patents license terminate if Facebook sues me for patent infringement first, and then I respond with a patent counterclaim against Facebook?

No, unless your patent counterclaim is related to Facebook's software licensed under the Facebook BSD+Patents license.

Does termination of the additional patent grant in the Facebook BSD+Patents license cause the copyright license to also terminate?

No.

From: https://code.facebook.com/pages/850928938376556

My reading must be off, then. Is "under any Necessary Claims" the magic phrase?

Yeah, it is defined at the bottom of the file:

> A "Necessary Claim" is a claim of a patent owned by Facebook that is necessarily infringed by the Software standing alone.

So when they say "license under any Necessary Claims" they are granting a patent license, the copyright license in the LICENSE file is separate.

The FAQ link provided by silentstreet makes it very clear:

> Does termination of the additional patent grant in the Facebook BSD+Patents license cause the copyright license to also terminate? > > No.

https://code.facebook.com/pages/850928938376556