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.