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

questions: 

\begin{enumerate}

\item How do 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 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 an set enumerated in GPLv3\S7. There

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.

% FIXME-LATER: It would be good to have detailed info on each of 7a-f.

%              Here's some commented-out text that might be useful for 7a-b

%% Under subsections 7a and 7b, the requirements may include preservation of

%% copyright notices, information about the origins of the code or alterations

%% of the code, and different warranty disclaimers. Under subsection 7c, the

%% requirements may include limitations on the use of names of contributors and

%% on the use of trademarks for publicity purposes. In general, we permit these

%% requirements in added terms because many free software licenses include them

%% and we consider them to be unobjectionable. Because we support trademark fair

%% use, the limitations on the use of trademarks may seek to enforce only what

%% is required by trademark law, and may not prohibit what would constitute fair

%% use.

% FIXME-LATER:  Say removing additional restrictions

% FIXME-LATER: This text may be useful later:

%% Some have questioned whether section 7 is needed, and some have suggested

%% that it creates complexity that did not previously exist.  We point out to

%% those readers that there is already GPLv2-licensed code that carries

%% additional terms.  One of the objectives of section 7 is to rationalize

%% existing practices of program authors and modifiers by setting clear

%% guidelines regarding the removal and addition of such terms.  With its

%% carefully limited list of allowed additional requirements, section 7

%% accomplishes additional objectives, permitting the expansion of the base of

%% code available for GPL developers, while also encouraging useful

%% experimentation with requirements we do not include in the GPL itself.

\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.

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 our license 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}

% FIXME-LATER: this is a punt: need more time to write!

GPLv3~\S10 ensures that everyone downstream receives licenses from all

copyright holders.  It really is a generally straightforward section.

% FIXME-LATER: link up this paragraph to above sections.

Note, however, GPLv3 removed the words ``at no charge'' from GPLv2~\S2(b) (in

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 practices 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