11. Patents.
A "contributor" is a copyright holder who authorizes use under this License of the Program or a work on which the Program is based. The work thus licensed is called the contributor's "contributor version".
A contributor's "essential patent claims" are all patent claims owned or controlled by the contributor, whether already acquired or hereafter acquired, that would be infringed by some manner, permitted by this License, of making, using, or selling its contributor version, but do not include claims that would be infringed only as a consequence of further modification of the contributor version. For purposes of this definition, "control" includes the right to grant patent sublicenses in a manner consistent with the requirements of this License.
Each contributor grants you a non-exclusive, worldwide, royalty-free patent license under the contributor's essential patent claims, to make, use, sell, offer for sale, import and otherwise run, modify and propagate the contents of its contributor version.
This is a "some companies might not want to have to litigate that". Whether or not there would be a problem is an open question. Legal likely advised not touching GPL version 3 out of an abundance of caution.
Eben Moglen speaking at the GPLv3 launch, January 16th 2006
...
We recognise that for parties who have extensive portfolios that are extensively cross-licensed, what we are saying here for the first time creates questions concerning their cross-licenses in relation to their distribution.
We recognise also that to say that you must "act to shield" is not explicit enough. We recognise that this is a very hard problem and though we have worked long at it we have no unique solution to offer you, even as a beginning for conversation.
...
I am not a lawyer, but what I understand from that is, if Apple authorizes use of bash under GPLv3, and then Apple decides it has a patent on something and bash is infringing on that patent, Apple can't go sue their customers for patent infringement because they are using bash. I'm 99% sure that's the intent of the clause. Lawyers are famously pessimistic and so I can see why they wouldn't want to test that, but seriously, what. are. the. chances.
Like seriously, maybe Oracle comes and sues Apple for patent infringement, and Apples only defense is to counter sue Oracle for using bash on their Macbooks?? They lost that defense when they stopped distributing bash, why not just distribute it under GPLv3 anyway?
As I understand it, it's more difficult than that... though I'm not a lawyer.
Let's say {some company} and Apple have a cross patent licensing for some set of patents.
Apple releases some softer under GPLv3. {Some company} sues someone else for a patent in bash. Since Apple licenses that patent and distributes bash, Apple is now obligated ("must act to shield") the distribution of bash that includes that patent.
If you distribute a covered work knowingly relying on a patent license, you must act to shield downstream users against the possible patent infringement claims from which your license protects you.
That wording of "knowingly relying on a patient license" and "must act to shield downstream users" are things that lawyers don't want to touch with a 10 foot pole. Would it mean that Apple would be required to defend the company that its patent partner is suing? Not a spot that lawyers want to be in. Furthermore, if you distribute GPLv3 software, it may mean that doing the cross patent licensing is more perilous... again, not a situation that lawyers or large companies want to be in.
There's Apple's bash distribution. If this was the GPLv3 version of bash and apple distributed a version that {some company} decided was infringing, and {some company} sued you - "I got it from Apple. Apple Legal, help me."
That's a helpful explanation, thank you. As a consumer of free software, that sounds great! I agree that it sounds pretty messy for big companies and all their patent deals. Sucks to be them, I guess
