Second, most technically-restricted User Products are designed to communicate

across networks.  It is important for both users and network providers to

know when denial of network access to devices running modified versions

becomes a GPL violation.  GPLv3 permits denial of access in two cases: ``when

the modification itself materially and adversely affects the operation of the

network,'' and when the modification itself ``violates the rules and

protocols for communication across the network''.  The second case is

deliberately drawn in general terms, and it serves as a foundation for

reasonable enforcement policies that respect recipients' right to modify

while recognizing the legitimate interests of network providers.

Note that GPLv3 permits the practice of conveying object code in a mode not

practically susceptible to modification by any party, such as code burned in

ROM or embedded in silicon.  The goal of the Installation Information

requirement is to ensure the downstream licensee receives the real right to

modify when the device manufacturer or some other party retains that right.

Accordingly, GPLv3\S6's ante-penultimate paragraph states that the

requirement to provide Installation Information ``does not apply if neither

you nor any third party retains the ability to install modified object code

on the User Product''.

Finally, GPLv3\S6 makes it clear that there is also no requirement to

provide warranty or support for the User Product itself.

\subsection{GPLv3~\S7: Additional Permissions}

\label{GPLv3s7}

The GPL is a statement of permissions, some of which have conditions.

Additional terms --- terms that supplement those of the GPL --- may come to be

placed on, or removed from, GPL-covered code in certain common ways.

Copyleft licensing theorists have generally called

 those added terms ``additional permissions'' if they grant

exceptions from the conditions of the GPL, and ``additional requirements'' if

they add conditions to the basic permissions of the GPL\@. The treatment of

additional permissions and additional requirements under GPLv3 is necessarily

asymmetrical, because they do not raise the same interpretive

issues; in particular, additional requirements, if allowed without careful

limitation, could transform a GPL'd program into a non-free one.

Due to the latter fear, historically,  GPLv2 did not permit any additional

requirements.  However, over time,

many copyright holders generally tolerated certain types of benign additional requirements

merely through a ``failure to enforce'' estoppel-esque scenario.  Therefore, GPLv3 allows

for some specific limited requirement variations that GPLv2 technically prohibits.

With these principles in the background, GPLv3~\S7  answers the following

questions: 

\begin{enumerate}

\item How does the presence of additional terms on all or part of a GPL'd program

affect users' rights?

\item When and how may a licensee add terms to code being

distributed under the GPL? 

\item When may a licensee remove additional terms?

\end{enumerate}

Additional permissions present the easier case.  Since the mid-1990s,

permissive exceptions often appeared alongside GPLv2 to allow combination

with certain non-free code.  Typically, downstream

stream recipients could remove those exceptions and operate under pure GPLv2.

Similarly, LGPLv2.1 is in essence a permissive variant of GPLv2,

and it permits relicensing under the GPL\@.  

These practices are now generalized via GPLv3~\S7.

A licensee may remove any additional permission from

a covered work, whether it was placed by the original author or by an

upstream distributor.  A licensee may also add any kind of additional

permission to any part of a work for which the licensee has, or can give,

appropriate copyright permission. For example, if the licensee has written

that part, the licensee is the copyright holder for that part and can

therefore give additional permissions that are applicable to it.

Alternatively, the part may have been written by someone else and licensed,

with the additional permissions, to that licensee.  Any additional

permissions on that part are, in turn, removable by downstream recipients.

As GPLv3~\S7\P1 explains, the effect of an additional permission depends on

whether the permission applies to the whole work or a part.

% FIXME-LATER: LGPLv3 will have its own section

Indeed, LGPLv3 is itself simply  a list of additional permissions supplementing the

terms of GPLv3.  GPLv3\S7 has thus provided the basis for recasting a

formally complex license as an elegant set of added terms, without changing

any of the fundamental features of the existing LGPL\@.  LGPLv3 is thus  a model for developers wishing to license their works under the

GPL with permissive exceptions.  The removability of additional permissions

under GPLv3\S7 does not alter any existing behavior of the LGPL since the LGPL

has always allowed relicensing under the ordinary GPL\@.

\section{GPLv3~\S7: Understanding License Compatibility}

\label{license-compatibility}

A challenge that faced the Free Software community heavily through out the

early 2000s was the proliferation of incompatible Free Software licenses.  Of

course, the GPL cannot possibly be compatible with all such licenses.

However, GPLv3

contains provisions that are designed to reduce license incompatibility by

making it easier for developers to combine code carrying non-GPL terms with

GPL'd code.

This license compatibility issue arises for

three reasons.  First, the GPL is a strong copyleft license, requiring

modified versions to be distributed under the GPL\@.  Second, the GPL states

that no further restrictions may be placed on the rights of recipients.

Third, all other software freedom respecting licenses in common use contain certain

requirements, many of which are not conditions made by the GPL\@.  Thus, when

GPL'd code is modified by combination with code covered by another formal

license that specifies other requirements, and that modified code is then

distributed to others, the freedom of recipients may be burdened by

additional requirements in violation of the GPL.  It can be seen that

additional permissions in other licenses do not raise any problems of license

compatibility.

GPLv3  took a new approach to the issue of combining GPL'd code with

code governed by the terms of other software freedom licenses.  Traditional

GPLv2 license compatibility theory (which was not explicitly stated in GPLv2

itself, but treated as a license interpretation matter by the FSF) held that GPLv2 allowed such

combinations only if the non-GPL licensing terms permitted distribution under

the GPL and imposed no restrictions on the code that were not also imposed by

the GPL\@.  In practice, the FSF historically supplemented that policy with a structure of

exceptions for certain kinds of combinations.

GPLv3~\S7  implements a more explicit policy on license

compatibility.  It formalizes the circumstances under which a licensee may

release a covered work that includes an added part carrying non-GPL terms. 

GPLv3~\S7 distinguish between terms that provide additional permissions, and terms that

place additional requirements on the code, relative to the permissions and

requirements established by applying the GPL to the code.

As discussed in the previous section of this tutorial, GPLv3~\S7 first and foremost explicitly allows added parts covered by terms with

additional permissions to be combined with GPL'd code. This codifies the

existing practice of regarding such licensing terms as compatible with the

GPL\@. A downstream user of a combined GPL'd work who modifies such an added

part may remove the additional permissions, in which case the broader

permissions no longer apply to the modified version, and only the terms of

the GPL apply to it.

In its treatment of terms that impose additional requirements, GPLv3\S7

extends the range of licensing terms with which the GPL is compatible.  An

added part carrying additional requirements may be combined with GPL'd code,

but only if those requirements belong to a set enumerated in GPLv3\S7. There

are, of course, limits on the acceptable additional requirements, which 

ensures that enhanced license compatibility does not

defeat the broader software-freedom-defending terms of the GPL\@. Unlike terms that grant

additional permissions, terms that impose additional requirements cannot be

removed by a downstream user of the combined GPL'd work, because only in the

pathological case\footnote{Theoretically, a user could collect copyright

  assignment from all known contributors and then do this, but this would

  indeed be the pathological case.}  would a user have the right to do so.

In general, the types of additional requirements were those terms in regular

use by other non-copyleft Free Software licenses that the FSF found

unobjectionable.  The specific details GPLv3's permitted additional

requirements hat GPLv3 are as follows:

\begin{enumerate}[label=7(\alph*):,ref=GPLv3s7\alph*]

\item This provision allows alternative ``disclaimer of warranty''

  forms. Copyright holders can disclaim warranty or limit liability

  differently from the terms as provided under GPLv3\S~\S15--16.  Drafters

  included this permission to advance the internationalization goals of

  GPLv3; international treaties lack adequate harmonization for laws

  regarding warranty and disclaimer.

\item This provision allows alternative requirements for preservation of

  appropriate legal notices.  GPLv3 permits additional requirements regarding

  preservation of legal notices, including on output from execution of

  covered works.  Preserved information can include information about the

  origins of the code or alterations of the code.

\item This provision allows prohibition of misrepresentation of original

  material.  The provision yields compatibility with non-copyleft Free

  Software licenses that require marking of modified versions in

  ``reasonable''ways which differ from GPL's own precise marking

  requirements.

\item This provision allows limitations on the use of names of licensor for

  publicity purposes.  This provision also yields additional compatibility

  with non-copyleft Free Software licenses that prohibit the use of the

  licensor's name on unmodified versions (or other prohibitions on

  advertising rights).  The third clause of the

  \href{http://opensource.org/licenses/BSD-3-Clause}{3-Clause BSD

  License}, for example, long considered de-facto compatible with GPLv2

    anyway, is via this clause unequivocally compatible with GPLv3.  However,

    \href{https://www.gnu.org/licenses/license-list.html#OriginalBSD}{this

      clause \textit{does not} make GPL compatible with the old BSD

      advertising clause} that the FSF

    \href{https://www.gnu.org/philosophy/bsd.html}{long ago identified as

      problematic}.

\item This provision clarifies that refusal to grant trademark rights for a

  GPLv3'd covered work remains compatible with GPLv3.  Again, some

  non-copyleft permissive licenses include such clauses.

\item This provision allows indemnification requirements of authors and

  licensors.  The FSF specifically designed this clause to achieve GPLv3

  compatibility for the

  \href{http://www.apache.org/licenses/LICENSE-2.0.html}{Apache Software

    License, Version 2.0}.

\end{enumerate}

During the GPLv3 drafting process, some questioned the necessity of GPLv3~\S7;

those critics suggested that it creates complexity that did not previously

exist.  However, by the time of GPLv3's drafting, many existing GPLv2'd

software packages already combined with various non-copylefted Free Software

licensed code that carried such additional terms.  Therefore, GPLv3~\S7 is

rationalized existing practices of those package authors and modifiers, since

it sets clear guidelines regarding the removal and addition of these

additional terms.  With its carefully limited list of allowed additional

requirements, GPLv3\S7 accomplishes additional objectives as well, since it

permits the expansion of the base of code available for GPL developers, while

also encouraging useful experimentation with requirements the GPLv3 does not

include by default.

However, any other non-permissive additional terms apart from those stated

above are considered ``further'' restrictions which

\hyperref[GPLv3s10]{GPLv3~\S10} prohibits.  Furthermore, as a compliance

matter, if you add additional terms in accordance with GPLv3~\S7, you must

ensure that the terms are placed in the relevant source files or provide a

conspicuous notice about where to find the additional terms.

\section{GPLv3~\S8: A Lighter Termination}

GPLv2 provided for automatic termination of the rights of a person who

copied, modified, sublicensed, or distributed a work in violation of the

license.  Automatic termination can be too harsh for those who have committed

an inadvertent violation, particularly in cases involving distribution of

large collections of software having numerous copyright holders.  A violator

who resumes compliance with GPLv2 technically needs to obtain forgiveness

from all copyright holders, and even contacting them all might be impossible.

GPLv3~\S8 now grants opportunities for provisional and permanent

reinstatement of rights. The termination procedure provides a limited

opportunity to cure license violations.  If a licensee has committed a

first-time violation of the GPL with respect to a given copyright holder, but

the licensee cures the violation within 30 days following receipt of notice

of the violation, then any of the licensee's GPL rights that have been

terminated by the copyright holder are ``automatically reinstated''.

Finally, if a licensee violates the GPL, a contributor may terminate any

patent licenses that it granted under GPLv3~\S11, in addition to any

copyright permissions the contributor granted to the licensee.

% FIXME-LATER: write more here, perhaps linking up to enforcement

\section{GPLv3~\S9: Acceptance}

GPLv3~\S9 means what it says: mere receipt or execution of code neither

requires nor signifies contractual acceptance under the GPL.  Speaking more

broadly, GPLv3 is intentionally structured as a unilateral grant

of copyright permissions, the basic operation of which exists outside of any

law of contract.  Whether and when a contractual relationship is formed

between licensor and licensee under local law do not necessarily matter to

the working of the license.

\section{GPLv3~\S10: Explicit Downstream License}

\label{GPLv3s10}

GPLv3~\S10 is a generally straightforward section that ensures that everyone

downstream receives licenses from all copyright holders.  Each time you

redistribute a GPL'd program, the recipient automatically receives a license,

under the terms of GPL, from every upstream licensor whose copyrighted

material is present in the work you redistribute.  You could think of this as

creating a three-dimensional rather than linear flow of license rights.

Every recipient of the work is ``in privity,'' or is directly receiving a

license from every licensor.

This mechanism of automatic downstream licensing is central to copyleft's

function.  Every licensor independently grants licenses, and every licensor

independently terminates the license on violation.  Parties further

downstream from the infringing party remain licensed, so long as they don't

themselves commit infringing actions.  Their licenses come directly from all

the upstream copyright holders, and are not dependent on the license of the breaching

party who distributed to them.  For the same reason, an infringer who acquires

another copy of the program has not thereby acquired any new license rights:

once any upstream licensor of that program has terminated the license for

breach of its terms, no new automatic license will issue to the recipient

just by acquiring another

copy\footnote{Footnote~\ref{German-reinstatement-footnote} also applies here

  in discussion of GPLv3 just as it did in discussion of GPLv2.}

Meanwhile, one specific addition in GPLv3 here in GPLv3~\S10 deserves special

mention.  Specifically, GPLv3 removed the words ``at no charge'' from

GPLv2~\S2(b) (which, BTW, became GPLv3~\S5(b)) because it contributed to a misconception that the GPL did not

permit charging for distribution of copies.  The purpose of the ``at no

charge'' wording was to prevent attempts to collect royalties from third

parties.  The removal of these words created the danger that the imposition

of licensing fees would no longer be seen as a license violation.  Therefore,

GPLv3~\S10 adds a new explicit prohibition on imposition of licensing fees or

royalties.  This section is an appropriate place for such a clause, since it

is a specific consequence of the general requirement that no further

restrictions be imposed on downstream recipients of GPL-covered code.

% FIXME-LATER: This text needs further study before I can conclude it belongs

% in this tutorial:

%% Careful readers of the GPL have suggested that its explicit prohibition

%% against imposition of further restrictions\footnote{GPLv2, section 6; Draft

%%   3, section 10, third paragraph.} has, or ought to have, implications for

%% those who assert patents against other licensees.  Draft 2 took some steps to

%% clarify this point in a manner not specific to patents, by describing the

%% imposition of ``a license fee, royalty, or other charge'' for exercising GPL

%% rights as one example of an impermissible further restriction.  In Draft 3 we

%% have clarified further that the requirement of non-imposition of further

%% restrictions has specific consequences for litigation accusing GPL-covered

%% programs of infringement.  Section 10 now states that ``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 the contribution of any contributor).''

%% That is to say, a patent holder's licensed permissions to use a work under

%% GPLv3 may be terminated under section 8 if the patent holder files a lawsuit

%% alleging that use of the work, or of any upstream GPLv3-licensed work on

%% which the work is based, infringes a patent.

\section{GPLv3~\S11: Explicit Patent Licensing}

\label{GPLv3s11}

Software patenting is a harmful and unjust policy, and should be abolished;

recent experience makes this all the more evident. Since many countries grant

patents that can apply to and prohibit software packages, in various guises

and to varying degrees, GPLv3 seeks to protect the users of GPL-covered programs

from those patents, while at the same time making it feasible for patent

holders to contribute to and distribute GPL-covered programs as long as they

do not attack the users of those programs.

It is generally understood that GPLv2 implies some limits on a licensee's

power to assert patent claims against the use of GPL-covered works.

However, the patent licensing practice that GPLv2~\S7 (corresponding to

GPLv3~\S12) is designed to prevent is only one of several ways in which

software patents threaten to make free programs non-free and to prevent users

from exercising their rights under the GPL. GPLv3 takes a more comprehensive

approach to combating the danger of patents.

GPLv2~\S7 has seen some success in deterring conduct that would otherwise

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.})

Some details of the ``essential patent claims'' definition deserve special

mention.  ``Essential patent claims'', for a given party, are a subset of the

claims ``owned or controlled'' by the party.  They do include sublicensable

claims that have been licensed to the contributor by a third

party.\footnote{This issue is typically handled in other software freedom

  licenses having patent licensing provisions by use of the unhelpful term

  ``licensable,'' which is either left undefined or is given an ambiguous

  definition.}  Most commercial patent license agreements that permit

sublicensing do so under restrictive terms that are inconsistent with the

requirements of the GPL\@.  For example, some patent licenses allow the

patent licensee to sublicense but require collection of royalties from any

sublicensees.  The patent licensee could not distribute a GPL-covered program

and grant the recipient a patent sublicense for the program without violating

section 12 of GPLv3.\footnote{GPLv3 also provides an example in section 12

  that makes this point clear.}  In rare cases, however, a conveying party

can freely grant patent sublicenses to downstream recipients without

violating the GPL\@.

Additionally, ``essential patent claims'' are those patents ``that would be

infringed by some manner, permitted by this License, of making, using, or

selling the work''.  This intends to make clear that a patent claim is

``essential'' if some mode of usage would infringe that claim, even if there

are other modes of usage that would not infringe.

Finally, ``essential patent claims \ldots do not include

claims that would be infringed only as a consequence of further

modification of the work.''  The set of essential patent

claims licensed  is fixed by the

particular version of the work that was contributed.  The claim set

cannot expand as a work is further modified downstream.  (If it could,

then any software patent claim would be included, since any software

patent claim can be infringed by some further modification of the

work.)\footnote{However, ``the work'' should not be understood to be

restricted to a particular mechanical affixation of, or medium for

distributing, a program, where the same program might be provided in

other forms or in other ways that may be captured by other patent claims

held by the contributor.}

\medskip

Ideally, this contributor patent policy will result in fairly frequent licensing of patent

claims by contributors.  A contributor is charged with awareness of the fact

that it has modified a work and provided it to others; no act of contribution

should be treated as inadvertent.  GPLv3's rule also requires no more work, for a

contributor, than the weaker rule proposed by the patent holders.  Under

their rule, the contributor must always compare the entire work against its

patent portfolio to determine whether the combination of the modifications

with the remainder of the work cause it to read on any of the contributor's

patent claims.

Finally, GPLv3's explicit patent license for contributors has an interesting

and useful side effect.  When a company with a large number of such claims

acquires the program's modifier, all claims held or thereafter acquired by

the purchaser are automatically licensed under this provision.  For example,

Microsoft's acquisition of Nokia resulted in the automatic licensing of all

Microsoft patent claims now or hereafter acquired which read on any

contributor version of any GPLv3 program ever modified by Nokia.

\subsection{Conveyors' Patent Licensing}

The remaining patent licensing in GPLv3 deals with patent licenses that are

granted by conveyance.  The licensing is not as complete or far reaching as

the contributor patent licenses discussed in the preceding section.

The term ``patent license,'' as used in GPLv3~\S11\P4--6, is not meant to be

confined to agreements formally identified or classified as patent licenses.

GPLv3~\S11\P3  makes this clear by defining ``patent

license,'' for purposes of the subsequent three paragraphs, as ``any express

agreement or commitment, however denominated, not to enforce a patent

(such as an express permission to practice a patent or covenant not to

sue for patent infringement)''

The definition does not include patent licenses that arise by

implication or operation of law, because the third through fifth paragraphs

of section 11 are specifically concerned with explicit promises that purport

to be legally enforceable. The final paragraph of section 11 explicitly

preserves the availability of patent licenses arising by implication or

operation of law.

GPLv3~\S11\P5 is commonly called GPLv3's downstream shielding provision.  It

responds particularly to the problem of exclusive deals between patent

holders and distributors, which threaten to distort the free software

distribution system in a manner adverse to developers and users.  The

fundamental idea is to make a trade-off between assuring a patent license for

downstream and making  (possibly patent-encumbered) CCS publicly available.

Simply put, in nearly all cases in which the ``knowingly relying'' test is

met, the patent license will indeed not be sublicensable or generally

available to all on free terms.  If, on the other hand, the patent license is

generally available under terms consistent with the requirements of the GPL,

the distributor is automatically in compliance, because the patent license

has already been extended to all downstream recipients.  Finally, if the

patent license is sublicensable on GPL-consistent terms, the distributor may

choose to grant sublicenses to downstream recipients instead of causing the

CCS to be publicly available.  (In such a case, if the distributor is also a

contributor, it will already have granted a patent sublicense anyway, and so

it need not do anything further to comply with the third paragraph.)

Admittedly, public disclosure of CCS is not necessarily required by other

sections of the GPL, and the FSF in drafting GPLv3 did not necessarily wish

to impose a general requirement to make source code available to all, which

has never been a GPL condition.  However, many vendors who produce products

that include copylefted software, and who are most likely to be affected by the

downstream shielding provision, lobbied for the addition of the source code

availability option, so it remains.

% FIXME-LATER: This text is likely redundant and a bit confusing.  Needs work

% to use.

%% If A takes a patent license from B that benefits A only, rather than A's

%% customers or their distributees, A imposes risk from B's patents on others

%% that it does not suffer itself. Under many circumstances, this is an

%% acceptable outcome. If, however, A is the only possible source of the

%% program, by taking such a license and distributing in reliance on it, A is in

%% effect helping B to ``take the program private.''

% FIXME-LATER: end

Meanwhile, two specific alternatives to the source code availability option

are also available. The distributor may comply by disclaiming the patent

license it has been granted for the conveyed work, or by arranging to extend

the patent license to downstream recipients.\footnote{The latter option, if

  chosen, must be done ``in a manner consistent with the requirements of this

  License''; for example, it is unavailable if extension of the patent

  license would result in a violation of GPLv3~\S 12.}  The GPL is intended

to permit private distribution as well as public distribution, and the

addition of these options ensures that this remains the case, even though it

remains likely that distributors in this situation will usually choose the

source code availability option.

Note that GPLv3~\S11\P5 is activated only if the CCS is not already otherwise

publicly available.  (Most often it will, in fact, already be available on

some network server operated by a third party.)  Even if it is not already

available, the option to ``cause the Corresponding Source to be so

available'' can then be satisfied by verifying that a third party has acted

to make it available.  That is to say, the affected distributor need not

itself host the CCS to take advantage of the source code availability option.

This subtlety may help the distributor avoid certain peculiar assumptions of

liability.

Note that GPLv3~\S11\P6--7 are designed to stop distributors from colluding with

third parties to offer selective patent protection.  GPLv3 is designed to

ensure that all users receive the same rights; arrangements that circumvent

this make a mockery of free software, and we must do everything in our power

to stop them.

First, GPLv3~\S11\P6 states that any license that protects some recipients of

GPL'd software must be extended to all recipients of the software.  

If conveyors arrange to provide patent

protection to some of the people who get the software from you, that

protection is automatically extended to everyone who receives the software,

no matter how they get it. 

Second, GPLv3~\S11\P7

prohibits anyone who made such an agreement from distributing software

released under GPLv3.  Conveyors are prohibited from

distributing software under GPLv3 if the conveyor makes an agreement of that

nature in the future.

The date in GPLv3~\S11\P7 likely seems arbitrary to those who did not follow

the GPLv3 drafting process.  This issue was hotly debated during the drafting of

GPLv3, but ultimately one specific deal of this type --- a deal between Microsoft

and Novell for Microsoft to provide so-called ``coupons'' to Microsoft customers to redeem

for copies of Novell's GNU/Linux distribution with a Microsoft patent license -- was

designed to be excluded.

The main reason for this was a tactical decision by the FSF.  FSF believed they can do more to

protect the community by allowing Novell to use software under GPLv3

than by forbidding it to do so.  This is because of

paragraph 6 of section 11 (corresponding to paragraph 4 in Draft 3).

It will apply, under the Microsoft/Novell deal, because of the coupons

that Microsoft has acquired that essentially commit it to participate

in the distribution of the Novell SLES GNU/Linux system.

The FSF also gave a secondary reason:  to avoid affecting other kinds of agreements for

other kinds of activities.  While GPLv3 sought to 

distinguish pernicious deals of the Microsoft/Novell type from

business conduct that is not particularly harmful, the FSF also did not

assume success in that drafting, and thus there remained some risk that other

unchangeable past agreements could fall within the  scope of GPLv3~\S11\P7.

In future deals, distributors engaging in ordinary business practices

can structure the agreements so that they do not fall under GPLv3~\S11\P7.

\section{GPLv3~\S12: Familiar as GPLv2~\S7}

\label{GPLv3s12}

GPLv2~\S12 remains almost completely unchanged from the text that appears in

GPLv2~\S7.  This is an important provision that ensures a catch-all to ensure

that nothing ``surprising'' interferes with the continued conveyance safely

under copyleft.

The wording in the first sentence of GPLv3~\S12 has been revised slightly to

clarify that an agreement -- such as a litigation settlement agreement or a

patent license agreement -- is one of the ways in which conditions may be

``imposed'' on a GPL licensee that may contradict the conditions of the GPL,

but which do not excuse the licensee from compliance with those conditions.

This change codifies the historical interpretation of GPLv2.

GPLv3 removed the limited severability clause of GPLv2~\S7 as a

matter of tactical judgment, believing that this is the best way to ensure

that all provisions of the GPL will be upheld in court. GPLv3 also removed

the final sentence of GPLv2 section 7, which the FSF consider to be unnecessary.

\section{GPLv3~\S13: The Great Affero Compromise}

The Affero GPL was written with the expectation that its

additional requirement would be incorporated into the terms of GPLv3

itself.  Many software freedom advocates, including some authors of this

tutorial, advocated heavily for that, and fully expected it to happen.

The FSF, however, chose not to include the Affero clause in GPLv3, due to

what it called  ``irreconcilable views from

different parts of the community''.  Many

commercial users of Free Software were opposed to the inclusion of a

mandatory Affero-like requirement in the body of GPLv3 itself.  In fact, some

wealthier companies even threatened to permanently fund forks of many FSF

copyrighted-programs under GPLv2 if the Affero clause appeared in GPLv3.

Meanwhile, there was disagreement even among copyleft enthusiasts about the

importance of the provision.  A coalition never formed, and ultimately the

more powerful interests implicitly allied with the companies who deeply opposed

the Affero clause such that the FSF felt the Affero clause would need its own

license, but one compatible with GPLv3. 

GPLv3~\S13 makes GPLv3 compatible with the AGPLv3, so that at least code can

be shared between AGPLv3'd and GPLv3'd projects, even if the Affero clause

does not automatically apply to all GPLv3'd works.

%FIXME-LATER:  no time to do this justice, will come back later, instead the

%above.

%% Some of this hostility seemed to be based on a misapprehension that

%% Affero-like terms placed on part of a covered work would somehow extend

%% to the whole of the work.\footnote{It is possible that the presence of

%% the GPLv2-derived copyleft clause in the existing Affero GPL contributed

%% to this misunderstanding.}  Our explanations to the contrary did little

%% to satisfy these critics; their objections to 7b4 instead evolved into a

%% broader indictment of the additional requirements scheme of section 7.

%% It was clear, however, that much of the concern about 7b4 stemmed from

%% its general formulation.  Many were alarmed at the prospect of GPLv3

%% compatibility for numerous Affero-like licensing conditions,

%% unpredictable in their details but potentially having significant

%% commercial consequences.

%% On the other hand, many developers, otherwise sympathetic to the policy

%% goals of the Affero GPL, have objected to the form of the additional

%% requirement in that license.  These developers were generally

%% disappointed with our decision to allow Affero-like terms through

%% section 7, rather than adopt a condition for GPLv3.  Echoing their

%% concerns about the Affero GPL itself, they found fault with the wording

%% of the section 7 clause in both of the earlier drafts.  We drafted 7b4

%% at a higher level than its Draft 1 counterpart based in part on comments

%% from these developers. They considered the Draft 1 clause too closely

%% tied to the Affero mechanism of preserving functioning facilities for

%% downloading source, which they found too restrictive of the right of

%% modification.  The 7b4 rewording did not satisfy them, however. They

%% objected to its limitation to terms requiring compliance by network

%% transmission of source, and to the technically imprecise or inaccurate

%% use of the phrase ``same network session.''

%% We have concluded that any redrafting of the 7b4 clause would fail to

%% satisfy the concerns of both sets of its critics.  The first group

%% maintains that GPLv3 should do nothing about the problem of public

%% use. The second group would prefer for GPLv3 itself to have an

%% Affero-like condition, but that seems to us too drastic. By permitting

%% GPLv3-covered code to be linked with code covered by version 2 of the

%% Affero GPL, the new section 13 honors our original commitment to

%% achieving GPL compatibility for the Affero license.

%% Version 2 of the Affero GPL is not yet published.  We will work with

%% Affero, Inc., and with all other interested members of our community, to

%% complete the drafting of this license following the release of Draft 3,

%% with a goal of having a final version available by the time of our

%% adoption of the final version of GPLv3.  We hope the new Affero license

%% will satisfy those developers who are concerned about the issue of

%% public use of unconveyed versions but who have concerns about the

%% narrowness of the condition in the existing Affero license.

%% As the second sentence in section 13 indicates, when a combined work is

%% made by linking GPLv3-covered code with Affero-covered code, the

%% copyleft on one part will not extend to the other part.\footnote{The

%% plan is that the additional requirement of the new Affero license will

%% state a reciprocal limitation.} That is to say, in such combinations,

%% the Affero requirement will apply only to the part that was brought into

%% the combination under the Affero license.  Those who receive such a

%% combination and do not wish to use code under the Affero requirement may

%% remove the Affero-covered portion of the combination.

Meanwhile, those who criticize the permission to link with code under the Affero

GPL should recognize that most other free software licenses also permit

such linking.  In particular, when a combined work is made by linking GPLv3-covered code

with AGPLv3-covered code, the copyleft on one part will not extend to the

other part. In such combinations, the Affero requirement will apply only to

the part originally brought into the combination under the Affero license.

In theory, those who receive such a combination and do not wish to use code

under the Affero requirement may remove the Affero-covered portion of the

combination.  (Admittedly, in practice, de-mingling of combined code can be

technically difficult.)

\section{GPLv3~\S14: So, When's GPLv4?}

\label{GPLv3s14}

No substantive change has been made in section 14. The wording of the section

has been revised slightly to make it clearer.

It's unclear when the FSF might consider publishing GPLv4.  However, this

section makes it clear that the FSF is the sole authority who can decide

such.

The main addition to this section allows a third-party proxy to be appointed

by contributors who wish someone else to make relicensing to new versions of

GPL when they are released.  This is a ``halfway'' point between using ``-only''

or ``-or-later'' by consolidating the decision-making on that issue to a

single authority.

% FIXME-LATER: better proxy description

\section{GPLv3~\S15--17: Warranty Disclaimers and Liability Limitation}

No substantive changes have been made in sections 15 and 16.

% FIXME-LATER: more, plus 17

% FIXME-LATER: Section header needed here about choice of law.

% FIXME-LATER: reword into tutorial

%% Some have asked us to address the difficulties of internationalization

%% by including, or permitting the inclusion of, a choice of law

%% provision.  We maintain that this is the wrong approach.  Free

%% software licenses should not contain choice of law clauses, for both

%% legal and pragmatic reasons.  Choice of law clauses are creatures of

%% contract, but the substantive rights granted by the GPL are defined

%% under applicable local copyright law. Contractual free software

%% licenses can operate only to diminish these rights.  Choice of law