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React.JS Developers Beware!

The React.js license is problematic in that licensees cannot sue Facebook for patent infringement (for any related or unrelated infringement), without losing the license to React.  In essence, by using React.js you grant Facebook the right to use (infringe) on your present and future patents.

React is licensed under BSD with a patent rider.  This means that Facebook, while granting patent rights, has also restricted the BSD license such that the terms are not the pure open source terms of the standard BSD license.  This patent rider has a "strong retaliation clause" which says that if you make any sort of patent claim against Facebook, the patent license automatically terminates- which means that Facebook can then sue you for patent infringement for using React.

Both Apache and GPL licenses have express patent license grants.  The BSD license does not, and though it’s not settle law, it’s generally considered that there is an implicit grant which cannot be revoked.  Facebook added an express patent license grant under the patent rider, but conditioned it on not suing Facebook for patent infringement, in any regard.  If you do, you lose the patent license, and likely the right to use React as may then be an integral part of your platform.

This means that if you use React, you may not be in a position to stop Facebook from leveraging your patents.  This should be an important part of any framework decision.

Further,  a potential acquirer of your company or software my look elsewhere, since an acquisition would imperil the acquirer’s patents as against Facebook, even if unrelated.  Google, Apple, Microsoft, and other big players may no longer have interest in your company as an acquisition target, unless your use of React.JS can be replaced - often a non-trivial or impossible task.

For reference, the relevant text from the React.js patent rider is:
The license granted hereunder will terminate, automatically and without notice, if you (or any of your subsidiaries, corporate affiliates or agents) initiate directly or indirectly, or take a direct financial interest in, any Patent Assertion: (i) against Facebook or any of its subsidiaries or corporate affiliates, (ii) against any party if such Patent Assertion arises in whole or in part from any software, technology, product or service of Facebook or any of its subsidiaries or corporate affiliates, or (iii) against any party relating to the Software. […]  A "Patent Assertion" is any lawsuit or other action alleging direct, indirect, or contributory infringement or inducement to infringe any patent, including a cross-claim or counterclaim.