While it's true that you only lose your license to the patents, not the code, I don't see how you can argue the grant isn't a restriction of your freedom? Surely any license whose conferred rights are predicated on the recipient not being able to take particular actions, up to and including saying particular things, must be considered to be restricting freedoms, even if those restrictions are in exchange for other freedoms granted?

Of course, all free software licenses involve some exchange of freedoms: You give up your ability to publish closed-source modifications of the software in exchange for being able to use and modify it at all. The question is whether the freedoms you are asked to give up are reasonable in exchange for what you gain. A patent grant that restricts your freedom to launch patent infringement litigation against other users of the software seem reasonable to me. Whereas a grant that is invalidated simply by alleging, through any action, that any of the original author's patents are invalid, does not.

So if you ever need to sue Facebook for patent infringement - you'll still be able to use React/React Native once they release it?

Are you saying that they could not come after you for simply using React (even if you were to dispute the relevant patents in court), or just that there is no evidence that they could?

Facebook cannot 'come after you' for using React if you have not accused them of patent infringement.

They can 'come after you' iff you have accused them of that, and you are using their software in such a way that a parent of theirs is violated.

It's pretty straightforward:

- Facebook has released some open source software. In the case of React, it's under the BSD license.

- You can use this software however you want, in accordance with the license.

- In addition to granting you a license to use the software, Facebook has granted you a license to any patents they own that cover the software.

- There is no enumeration or claim that any patents do cover the software.

- Your license to use any hypothetical patent that does cover the software will be revoked if you make a claim—legal or otherwise—that Facebook has infringed any patent.

- At that point, you will no longer have a license to use any patent that covers the software.

- If you are subsequently using the software in a way that infringes one of their patents, Facebook would legitimately be able to claim patent infringement.