result in denial of full downstream enjoyment of GPL rights, and thus it is

preserved in GPLv3~\S12.  Experience has shown that more is necessary,

however, to ensure adequate community safety where companies act in concert

to heighten the anticompetitive use of patents that they hold or license.

Therefore,  GPLv3 is designed to reduce the patent risks that distort and

threaten the activities of users who make, run, modify and share Free

Software.  At the same time, GPLv3 gives favorable consideration to practical

goals such as certainty and administrability for patent holders that

participate in distribution and development of GPL-covered software.  GPLv3's

policy requires each such patent holder to provide appropriate levels of

patent assurance to users, according to the nature of the patent holder's

relationship to the program.

In general, GPLv3 provides for two classes of patent commitments:

\begin{itemize}

\item Grant of license to claims in contributor versions: GPLv3~\S11

  introduces an affirmative grant of rights to patent claims by those who

  contribute code to GPL'd programs. The intent is to prevent parties from

  aggressively asserting patents against users of code those parties have

  themselves modified --- in theory preventing betrayal by ``insiders'' of

  the copyleft community.  A contributor's patent claims necessarily

  infringed by the version of the program created by the incorporation of its

  modifications are licensed to all subsequent users and modifiers of the

  program, or programs based on the program.  No patent claims only infringed

  by subsequent modifications by other parties are thus licensed.  Patent

  claims acquired after the making of the ``contributor version'' necessarily

  infringed by that version are also licensed by this provision at the time

  of their acquisition or perfection.

\item Prohibition of enforcement of patent claims against those to whom you

  distribute: GPLv3~\S10 makes explicit that licensees who directly

  distribute may not make demands for acceptance of patent licenses or

  payment of patent royalties from distribution recipients.  This provision

  establishes a uniform rule of patent exhaustion with respect to GPL'd

  programs regardless of the domestic patent law in any particular system or

  locale.

\end{itemize}

The following two subsections discuss in order each of the above mentioned

classes of patent commitments.

\subsection{The Contributor's Explicit Patent License}

Specifically, the ideal might have been for GPLv3 to feature a patent license

grant triggered by all acts of distribution of GPLv3-covered works.  The FSF

considered it during the GPLv3 drafting process, but many patent-holding

far-reaching impact of the patent license grant on the patent holder is

disproportionate to the act of merely distributing code without modification

patent assets to exercise requisite diligence in reviewing all the

GPL-covered software that it provides to others.  Some expressed particular

concern about the consequences of ``inadvertent'' distribution.

The argument that the impact of the patent license grant would be

``disproportionate'',  that is to say unfair, is not valid. Since

software patents are weapons that no one should have, and using them for

aggression against free software developers is an egregious act (thus

preventing that act cannot be unfair). 

However, the second argument seems valid in a practical sense.  A

typical GNU/Linux distribution includes thousands of programs.  It would

be quite difficult for a re-distributor with a large patent portfolio to

review all those programs against that portfolio every time it receives

and passes on a new version of the distribution.  Moreover, this question

raises a strategic issue. If the GPLv3 patent license requirements

convince patent-holding companies to remain outside the distribution

path of all GPL-covered software, then these requirements, no matter how

strong, will cover few patents. 

GPLv3 therefore makes a partial concession

which would lead these companies to feel secure in doing the

distribution themselves. GPLv3~\S11

applies only to those distributors that have

modified the program.  The other changes we have made in sections 10 and

11 provide strengthened defenses against patent assertion and compensate

partly for this concession. 

Therefore, GPLv3~\S11 introduces the terms ``contributor'', ``contributor version'', and

``essential patent claims'', which are

used in the GPLv3~\S11\P3.   Viewed from the perspective of a recipient of the

Program, contributors include all the copyright holders for the Program,

other than copyright holders of material originally licensed under non-GPL

terms and later incorporated into a GPL-covered work.  The contributors are

therefore the initial GPLv3 licensors of the Program and all subsequent

upstream licensors who convey, under the terms of GPLv3~\S5, modified covered

works.

Thus, the ``contributor version'' includes the material the contributor has copied from the

upstream version that the contributor has modified.  GPLv3~\S11\P3

 does not apply to those that redistribute the program

without change.\footnote{An implied patent license from the distributor,

however, often arises.  See \S~\ref{gpl-implied-patent-grant} in this tutorial}

In other words, the ``contributor version'' includes not just

the material added or altered by the contributor, but also the pre-existing

material the contributor copied from the upstream version and retained in the

modified version.  (GPLv3's usage of ``contributor'' and ``contribution'' should

not be confused with the various other ways in which those terms are used in

certain other free software licenses.\footnote{Cf., e.g., Apache License,

  version 2.0, section 1; Eclipse Public License, version 1.0, section 1;

  Mozilla Public License, version 1.1, section 1.1.})