There was this explanation from an HN user: <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=8901357" rel="nofollow">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=8901357</a><p>But Facebook made changes since then: <a href="http:&#x2F;&#x2F;www.infoworld.com&#x2F;article&#x2F;2908879&#x2F;open-source-software&#x2F;facebook-gives-in-on-patent-grant.html" rel="nofollow">http:&#x2F;&#x2F;www.infoworld.com&#x2F;article&#x2F;2908879&#x2F;open-source-softwar...</a><p>I don&#x27;t know much about it, just giving you links.