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Implicit patent licence

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An implicit patent licence is a licence (grant of permission) created by the actions or words of an entity distributing software, even if nothing explicitly mentions permission to use any patents. The logic is that when you give someone a tool, you are implying that they can use it without you suing them.

However, there is debate (and little or no case law) about how broad this implicit licence is for software. At a minimum, it would seem to apply to use of software as published (i.e. without modifying the source code), for foreseen purposes.

As discussed below, free software licences may have a broader implicit licence (or a separate "semi-explicit" licence).

European Union

The following was written by a lawyer from the European Commission, talking about GPL version 2:

Suppose, for example, that the owner of MySQL has a patent with a claim Z covering a software feature and MySQL implements this software feature and releases the implementation under the GPL. Any licensee would indeed, as the notifying party has argued repeatedly during the proceedings, essentially receive an irrevocable patent-license comprised within the GPL. However, this implicit license would be limited to the use that is being made of the patent claim by the code as originally released under the GPL. If the licensee now changes the code in a way that adds another use or implementation of claim Z it may be liable for patent infringement as regards the code it has added to what it had originally received under the GPL.[1]

(emphasis added)

The lawyer doesn't mention whether this implied licence is created when any software is distributed, or when any free software is distributed (see below), or if it is specific to GPL version 2.


In 2005, Dan Ravicher explained[2] that, in the USA, recipients of software under the GNU GPL version 2 receive an implicied patent grant, based on the following US case law.

(Emphasis added by Dan.)

  • De Forest Radio, 273 U.S. 236 (1927)

No formal granting of a license is necessar y in order to give it effect. Any language used by the owner of the patent, or any conduct on his part exhibited to another from which that other may properly infer that the owner consents to his use of the patent in making or using it, or selling it, upon which the o ther acts, constitutes a license.”

  • Hewlett - Packard Co. v . Repeat - O-Type Stencil Mfg. Corp. , Inc., 123 F. 3d 1445 (Fed. Cir. 1997).

Generally, when a seller sells a product without restriction, it in effect promises the purchaser that in exchange for the price paid, it will not interfere wit h the purchaser's full enjoyment of the product purchased. The buyer has an implied license under any patents of the seller that dominate the product or any uses of the product to which the parties might reasonably contemplate the product will be put.

  • Bottom Line Mgmt., Inc. v. Pan Man, Inc., 228 F. 3d 1352 (Fed. Cir. 2000)

Unless the parties provide otherwise, the purchaser of a patented article has an implied license not only to use and sell it, but also to repair it to enable it to function properly. This implied license covers both the original purchaser of the article and all subsequent purchasers.

Scope in the US

Eben Moglen, in a 2009 submission to the European Commission, gave his evaluation regarding the situation in the USA:[3]

In this connection, I would be more cautious about the legal conclusion reached in SO 765, involving the example of feature Z, placed in a copy of a GPLv2 MySQL distributed by Oracle, and then reimplemented a second time, elsewhere in the MySQL codebase by a subsequent modifier. The conclusion drawn may be correct under one or more patent systems, but in my own, I am doubtful. If, for example, we were talking about a literal copy of the patent-covered code duplicated from one portion of the codebase to another, I very much doubt that the second invocation of the same code could be patent infringing, while the first is covered by implicit license. In any event, the implicit license is to use the patent claims, and it is hard to see how the license to use could fail to cover both copies. Whether the provision of a second literal copy of the code constituted “making,” would I suppose hinge at most on whether the code was actually duplicated, or was turned into a subroutine called from more than one location. In any event, I would not expect the threat of such a patent infringement action to be taken seriously by any US party engaged in modifying the code.

In free software licences

See also: Patent clauses in software licences

In addition, it's possible that free software licences provide a stronger implied licence. Unlike licences for non-free software, which focus on listing what the recipient may not do, free software licences contain clear statements about what the user may do. This might mean that in addition to the act of distributing the software (which was sufficient for the above-mentioned rulings in the USA), the intent of the distributor can be read in the licence.

A very minimal example would be the MIT/X11 licence, which says: "Permission is hereby granted (...) to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so".

If this is shown to a judge, it would be difficult for the patent holder to argue that they never intended to give permission for the recipient to use or distribute the software. The MIT/X11 licence says it gives "permission" - not just "copyright permission".

A stronger example would be the GNU GPLv2. (See sections 6 and 7.)

Then finally there are licences such as Apache-2, MPL-2, and GPLv3 which contain explicit patent grants. People using this software should have no need of the implied licence.

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