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Patent clauses in software licences
Software licences can solve a small category of patent problems. They can:
- require that distributors of a software package give recipients a licence to use any necessary patents, and
- make patent aggression less attractive by revoking patent rights that any aggressor received through the licence
- GPLv3 (if looking for a "strong copyleft" licence)
- LGPLv3 (if looking for a "weak copyleft" licence)
- Apache 2 (if looking for a "permissive" licence)
Each of these is discussed below.
 Limits to effectiveness
- These clauses only apply to patent holders who distribute the software which uses this licence.
- The stronger the clause, the less likely it is that dangerous patent holders will distribute software that uses the licence.
 How to evaluate patent clauses
Good patent clauses that can be put into software licences include:
- A grant of patent rights
- An example of a very good grant is GPLv3, which causes distributors of modified versions to grant an explicit patent licence for the whole program. Next in line would be the Apache License 2.0, which also has an explicit grant, but only for the changes made by that distributor. Lower down the list comes GPLv2, which has no explicit patent grant but does talk about patents and causes distributors to pass on permission to use/modify/redistribute, thus forming an implicit patent grant. Obviously, worst of all are the licences which contain no patent grant.
- Retract the granted rights from anyone who initiates litigation. This allows the distributor to use their patents to defend against aggression.
- This would be great, but it's usually impractical.
 GNU GPL v2
- (See: GPLv2 and patents)
 GNU GPL v3
Note: the same patents clause exists in the: GNU Affero General Public License v3
you may not impose a license fee, royalty, or other charge for exercise of rights granted under this License, and you may not initiate litigation (including a cross-claim or counterclaim in a lawsuit) alleging that any patent claim is infringed by making, using, selling, offering for sale, or importing the Program or any portion of it.
Also, section 12, which is very similar to GPLv2's section 7.
 Related discussions
- From the 25th minute onward, Bradely Kuhn explains GPLv3 section 11
 LGPL 2.1
- Discussion about Google's Chrome using LGPL'd library and having a patent licence, Chris DiBona gives Google's position
 Apache License 2.0
The Apache License contains both a patent grant and a patent retaliation clause. The retaliation clause, written in 2004, was copied by the GNU GPLv3 and the MPL 2.0,
The grant is the first half of Section 3:
Subject to the terms and conditions of this License, each Contributor hereby grants to You a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable (except as stated in this section) patent license to make, have made, use, offer to sell, sell, import, and otherwise transfer the Work, where such license applies only to those patent claims licensable by such Contributor that are necessarily infringed by their Contribution(s) alone or by combination of their Contribution(s) with the Work to which such Contribution(s) was submitted.
The retaliation clause is the second half of that section:
If You institute patent litigation against any entity (including a cross-claim or counterclaim in a lawsuit) alleging that the Work or a Contribution incorporated within the Work constitutes direct or contributory patent infringement, then any patent licenses granted to You under this License for that Work shall terminate as of the date such litigation is filed.
The patent provisions of the Common Public License (CPL) and Eclipse Public License (EPL) are described by Mark Webbink as "quite similar to that of the Apache License, version 2."
 Mozilla Public License
- (Main article: MPL and patents)
 WebM licence
Google first published the WebM audio-video codec under a licence which had a patent grant and a retaliation clause. After some unrelated controversy, they changed to a simpler licence and a separate grant.
Google hereby grants to you a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable (except as stated in this section) patent license to make, have made, use, offer to sell, sell, import, transfer, and otherwise run, modify and propagate the contents of this implementation of VP8, where such license applies only to those patent claims, both currently owned by Google and acquired in the future, licensable by Google that are necessarily infringed by this implementation of VP8. This grant does not include claims that would be infringed only as a consequence of further modification of this implementation.
That last line was added by Google in June when the text was changed from being part of the licence to being a separate grant.
The retaliation clause:
If you or your agent or exclusive licensee institute or order or agree to the institution of patent litigation against any entity (including a cross-claim or counterclaim in a lawsuit) alleging that this implementation of VP8 or any code incorporated within this implementation of VP8 constitutes direct or contributory patent infringement, or inducement of patent infringement, then any patent rights granted to you under this License for this implementation of VP8 shall terminate as of the date such litigation is filed.
- (Main article: CDDL and patents)
 Related pages on en.swpat.org
- Duds and non-solutions
- Free software - practically all discussion of such clauses is in relation to free software licences
- Patent promises
- CDDL and patents
- GPLv2 and patents
- Packaging Open Source, a paper which looks briefly at the patent clauses of various free software licences, by Mark Webbink, December 2009
- A forum comment describing a possible limit to the effectiveness of licences
- Comparison of software licence clauses and promises, (audio) by Bradley Kuhn
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