never be required to provide more than that.  One always has the right to

modify a source code work by deleting any part of it, and there can be no

requirement that free software source code be a whole functioning program.

\section{The System Library Exception}

The previous section skipped over one part of the CCS definition, the

so-called system library exception.  The ``System Libraries'' definition (and

the ``Standard Interface'' and ``Major Component'' definitions, which it

includes) are designed as part

to permit certain distribution arrangements that are considered reasonable by

copyleft advocates.  The system library exception is designed to allow

copylefted software to link with these libraries when such linking would hurt

software freedom more than it would hurt proprietary software.

The system library exception has two parts.  Part (a) rewords the GPLv2

exception for clarity replaces GPLv2's words ``unless that component itself

accompanies the executable'' with ``which is not part of the Major

Component''.  The goal here is to not require disclosure of source code of

certain libraries, such as necessary Microsoft Windows DLLs (which aren't

part of Windows' kernel but accompany it) that are required for functioning

of copylefted programs compiled for Windows.

However, in isolation, (a) would be too permissive, as it would sometimes

allowing distributors to evade important GPL requirements.  Part (b) reigns

in (a).  Specifically, (b) specifies only a few functionalities that a the

system library may provide and still qualify for the exception.  The goal is

to ensure system libraries are truly adjunct to a major essential operating

system component, compiler, or interpreter.  The more low-level the

functionality provided by the library, the more likely it is to be qualified

for this exception.

Admittedly, the system library exception is a frequently discussed topic of

obsessed GPL theorists.  The amount that has been written on the system

library exception (both the GPLv2 and GPLv3 versions of it), if included

herein,  could easily increase this section of the tutorial to a length

greater than all the others.

Like any exception to the copyleft requirements of GPL, would-be GPL

violators frequently look to the system library exception as a potential

software freedom circumvention technique.  When considering whether or not a

library qualifies for the system library exception, here is a pragmatic

thesis to consider, based on the combined decades of experience in GPL

interpretation of this tutorial's authors: the harder and more strained the

reader must study and read the system library exception, the more likely it

is that the library in question does not qualify for it.

\section{GPLv3~\S2: Basic Permissions}

% FIXME: phrase ``unmodified Program'' appears due to User Products exception

We have included the first sentence of section 2 to further internationalize

the GPL. Under the copyright laws of some countries, it may be necessary for

a copyright license to include an explicit provision setting forth the

duration of the rights being granted. In other countries, including the

United States, such a provision is unnecessary but permissible.

The first paragraph of section 2 also acknowledges that licensees under the

GPL enjoy rights of copyright fair use, or the equivalent under applicable

law. These rights are compatible with, and not in conflict with, the freedoms

that the GPL seeks to protect, and the GPL cannot and should not restrict

them.

% FIXME: propagate and convey

Section 2 distinguishes between activities of a licensee that are permitted

without limitation and activities that trigger additional requirements. The

second paragraph of section 2 guarantees the basic freedoms of privately

modifying and running the program. However, the right to privately modify and

run the program is terminated if the licensee brings a patent infringement

lawsuit against anyone for activities relating to a work based on the

program.

% FIXME:  transition, and some word smith

The explicit prohibition of sublicensing ensures that enforcement of the GPL

is always by the copyright holder.  Usually, sublicensing is regarded as a

practical convenience or necessity for the licensee, to avoid having to

negotiate a license with each licensor in a chain of distribution.  The GPL

solves this problem in another way, through its automatic licensing

provision.

% FIXME: new section here, just to talk DRM before the other section.

GPLv3 introduces provisions that respond to the growing practice of

distributing GPL-covered programs in devices that employ technical means

to restrict users from installing and running modified versions.  This

practice thwarts the expectations of developers and users alike, because

the right to modify is one of the core freedoms the GPL is designed to

secure.

Technological measures to defeat users' rights --- often described by such

Orwellian phrases as ``digital rights management,'' which actually means

limitation or outright destruction of users' legal rights, or ``trusted

computing,'' which actually means selling people computers they cannot trust

--- are alike in one basic respect.  They all employ technical means to turn

litigation in violation of section 10.

We have made two substantive changes to section 8.  First, we have clarified

that patent rights granted under the GPL are among the rights that a

copyright holder may terminate under section 8.  Therefore, a contributor who

grants a patent license under the first paragraph of section 11 may terminate

that patent license, just as that contributor may terminate copyright rights,

to a downstream recipient who has violated the license.  We think that this

is a reasonable result, and was already implicit in the wording of the

termination provision in our earlier drafts.  Moreover, this clarification

should encourage patent holders to make contributions to GPL-covered

programs.

Second, we have modified the termination procedure by providing a limited

opportunity to cure license violations, an improvement that was requested by

many different members of our community.  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.''  The

addition of the cure opportunity achieves a better balance than our earlier

section 8 drafts between facilitating enforcement of the license and

protecting inadvertent violators against unfair results.

We have restructured the form of section 8 by replacing non-automatic

termination with automatic termination coupled with opportunities for

provisional and permanent reinstatement of rights.  The revised wording does

not alter the underlying policy or details of procedure established in the

previous drafts, including the 60-day period of repose and 30-day cure

opportunity for first-time violators.  The restoration of automatic

termination was motivated in part to facilitate enforcement in European

countries.  We also believe the revised wording will be easier to understand

and apply in all jurisdictions.

\section{GPLv3~\S9: Acceptance}

% FIXME: needs some work here

Section 9 means what it says: mere receipt or execution of code neither

requires nor signifies contractual acceptance under the GPL.  Speaking more

broadly, we have 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: needs filled out and more here.

Draft1 removed the words ``at no charge'' from what is now subsection 5b, the

core copyleft provision, for reasons related to our current changes to the

second paragraph of section 4: it had 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.

We therefore have added a new explicit prohibition on imposition of licensing

fees or royalties in section 10.  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.

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}

The patent licensing practices that section 7 of GPLv2 (corresponding to

section 12 of GPLv3) was designed to prevent are 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 combatting the danger of patents.

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, we seek to protect the users of GPL-covered programs