The clause also doesn't explicitly cover software patents only, so if Facebook infringes on your hardware patents (which is plausible, since Facebook does hardware related work as well), you still can't sue them.
It might as well say "we agree to not destroy your business using dirty tricks if you don't attempt the same".
Of course, opinions on that are divided...
This is an oversimplification. There are plenty of mum and dad inventors who would get destroyed by large companies but for relying on patent protection for their life's work.
Why should Facebook support companies that are suing them?
If they were offering something unique or especially distinctive, then maybe it would be worth risking, but as there are half a dozen or so alternatives, why bother putting myself into that particular pickle?
This doesn't prevent you from suing. It just prevents you from suing over patents.
I can understand why Facebook would want to have a clause like this (to discourage lawsuits against them), but I would consider it against the spirit of open source to do so (ie. Facebook should be able to continue to do this, but I wouldn't consider React to be open source software in that case).
I guess the GPLv3 has provisions for patents, but older licenses didn't. I remember some controversy around open source video codecs that you were not able to use safely because they were infringing patents.
GPLv2 didn't have a patent grant because it wasn't a very well-known issue in 1991. Apache 2.0 was the first free software license to have a patent grant (which unfortunately made it GPLv2 incompatible) but GPLv3 included a similar (though stronger) patent grant because of Apache 2.0.
While these may sound like theoretical problems, people have been sued over using GIF, MP3, etc before. Every time you install Firefox, it will download a free software binary from a Cisco server that does h264 decoding[5]. However, they cannot legally recompile the binaries themselves as it means that the patent grant no longer applies and Mozilla (or your distribution) could be sued -- even though the binary's source is BSD-licensed.
[1]: https://www.gnu.org/philosophy/fighting-software-patents.htm... [2]: https://www.gnu.org/philosophy/danger-of-software-patents.ht... [3]: https://www.fsf.org/licensing/h264-patent-license [4]: https://www.iis.fraunhofer.de/en/ff/amm/prod/audiocodec/audi... [5]: http://www.openh264.org/index.html
Where does it say what? Which part of my post are you taking issue with, because I would love to correct anything.
What it certainly doesn't say is that Facebook's patent portfolio is non-aggressive. And when, outside of this, has Facebook said that about their entire portfolio (I'm not saying they haven't, I just haven't seen that before)?
Now where does it say that? The way I read it, so long as you don't sue Facebook, you have a patent grant. If you believe people when they say that their patent portfolios are purely defensive, there is no problem.
On the other hand, being the aggressor in a patent lawsuit loses you the patent grant. This seems sane enough to me.
The normal state of affairs is completely ambiguous about patents. You get no explicit grant, so if they feel like suing, there's nothing to stop them. Some people claim an implicit grant, but there's no conclusive ruling on it.
I don't particularly care for software patents, but I don't see anything more stupid than the usual lawyerly CYA layered on an attempt to disambiguate the patent situation.