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.
https://fsfe.org/activities/gplv3/patents-and-gplv3.en.html#...
Eben Moglen speaking at the GPLv3 launch, January 16th 2006
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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.
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