pillar of altruistic sharing of improved Free Software. Historically

it was typical for a

Free Software project to sprout a mailing list where improvements

would be shared

freely among members of the development community\footnote{This is still

commonly the case, though today there are other or additional ways of

sharing Free Software.}.   Such noncommercial

sharing is the primary reason that Free Software thrives.

Commercial sharing of modified Free Software is equally important.

For commercial support to exist in a competitive free market, all

developers -- from single-person contractors to large software

companies -- must have the freedom to market their services as

augmenters of Free Software.  All forms of such service marketing must

be equally available to all.

For example, selling support services for Free Software is fully

permitted. Companies and individuals can offer themselves as ``the place

to call'' when software fails or does not function properly.  For such a

service to be meaningful, the entity offering that service needs the

right to modify and improve the software for the customer to correct any

problems that are beyond mere user error.

Software freedom licenses also permit any entity to distribute modified

versions of Free Software.  Most Free Software programs have a ``standard

version'' that is made available from the primary developers of the software.

However, all who have the software have the ``freedom to fork'' -- that is,

make available nontrivial modified versions of the software on a permanent or

semi-permanent basis.  Such freedom is central to vibrant developer and user

interaction.

Companies and individuals have the right to make true value-added versions

of Free Software.  They may use freedom to share improvements to

distribute distinct versions of Free Software with different functionality

and features.  Furthermore, this freedom can be exercised to serve a

disenfranchised subset of the user community.  If the developers of the

standard version refuse to serve the needs of some of the software's

users, other entities have the right to create a long- or short-lived fork

to serve that sub-community.

\section{How Does Software Become Free?}

The previous section set forth key freedoms and rights that are referred to

as ``software freedom''.  This section discusses the licensing mechanisms

used to enable software freedom.  These licensing mechanisms were ultimately

created as a community-oriented ``answer'' to the existing proprietary

software licensing mechanisms.  Thus, first, consider carefully why

proprietary software exists in the first place.

\label{explaining-copyright}

The primary legal regime that applies to software is copyright law.

Proprietary software exists at all only because copyright law governs

software.\footnote{This statement is admittedly an oversimplification. Patents and

  trade secrets can cover software and make it effectively non-Free, and one

  can contract away their rights and freedoms regarding software, or source

  code can be practically obscured in binary-only distribution without

  reliance on any legal system.  However, the primary control mechanism for

  software is copyright, and therefore this section focuses on how copyright

  restrictions make software proprietary.} Copyright law, with respect to

software, typically governs copying, modifying, and redistributing that

software (For details of this in the USA, see

\href{http://www.copyright.gov/title17/92chap1.html#106}{\S~106} and

\href{http://www.copyright.gov/title17/92chap1.html#117}{\S~117} of

\href{http://www.law.cornell.edu/uscode/text/17}{Title 17} of the

\textit{United States Code}).\footnote{Copyright law in general also governs

  ``public performance'' of copyrighted works. There is no generally agreed

  definition for public performance of software and both GPLv2 and GPLv3 do

  not restrict public performance.} By law (in the USA and in most other

jurisdictions), the copyright holder (most typically, the author) of the work controls

how others may copy, modify and/or distribute the work. For proprietary

software, these controls are used to prohibit these activities. In addition,

proprietary software distributors further impede modification in a practical

sense by distributing only binary code and keeping the source code of the

software secret.

Copyright is not a natural state, it is a legal construction. In the USA, the

Constitution permits, but does not require, the creation of copyright law as

federal legislation.  Software, since it is an ``original work of authorship

fixed in any tangible medium of expression ...  from which they can be

perceived, reproduced, or otherwise communicated, either directly or with the

aid of a machine or device'' (as stated in

\href{http://www.law.cornell.edu/uscode/text/17/102}{17 USC \S~102}), is thus

covered by the statute, and is copyrighted by default.

However, software, in its natural state without copyright, is Free

Software. In an imaginary world with no copyright, the rules would be

different. In this world, when you received a copy of a program's source

code, there would be no default legal system to restrict you from sharing it

with others, making modifications, or redistributing those modified

versions.\footnote{Note that this is again an oversimplification; the

  complexities with this argument are discussed in

  Section~\ref{software-and-non-copyright}.}

Software in the real world is copyrighted by default and is automatically

covered by that legal system.  However, it is possible to move software out

of the domain of the copyright system.  A copyright holder can often

\defn{disclaim} their copyright. (For example, under USA copyright law

it is possible for a copyright holder to engage in conduct resulting

in abandonment of copyright.)  If copyright is disclaimed, the software is

effectively no longer restricted by copyright law.   Software not restricted by copyright is in the

``public domain.''

\subsection{Public Domain Software}

In the USA and other countries that

are parties to the Berne Convention on Copyright, software is copyrighted

automatically by the author when she fixes the software in a tangible

medium.  In the software world, this usually means typing the source code

of the software into a file.

Imagine if authors could truly disclaim those default controls of copyright

law.  If so, the software is in the public domain --- no longer covered by

copyright.  Since copyright law is the construction allowing for most

restrictions on software (i.e., prohibition of copying, modification, and

redistribution), removing the software from the copyright system usually

yields software freedom for its users.

Carefully note that software truly in the public domain is \emph{not} licensed

in any way.  It is confusing to say software is ``licensed for the

public domain,'' or any phrase that implies the copyright holder gave

express permission to take actions governed by copyright law.

Copyright holders who state that they are releasing their code into

the public domain are effectively renouncing copyright controls on

the work.  The law gave the copyright holders exclusive controls over the

work, and they chose to waive those controls.  Software that is, in

this sense, in the public domain

is conceptualized by the developer as having no copyright and thus no license. The software freedoms discussed in

Section~\ref{Free Software Definition} are all granted because there is no

legal system in play to take them away.

Admittedly, a discussion of public domain software is an oversimplified

example.  

Because copyright controls are usually automatically granted and because, in

some jurisdictions, some copyright controls cannot be waived (see

Section~\ref{non-usa-copyright} for further discussion), many copyright

holders sometimes incorrectly believe a work has been placed in the public

domain.  Second, due to aggressive lobbying by the entertainment industry,

the ``exclusive Right'' of copyright, that was supposed to only exist for

``Limited Times'' according to the USA Constitution, appears to be infinite:

simply purchased on the installment plan rather than in whole.  Thus, we must

assume no works of software will fall into the public domain merely due to

the passage of time.

Nevertheless, under USA law it is likely that the typical

disclaimers of copyright or public domain dedications we see in the

Free Software world would be interpreted by courts as copyright

abandonment, leading to a situation in which the user effectively receives a

maximum grant of copyright freedoms, similar to a maximally-permissive

Free Software license.

The best example of software known to truly be in the public domain is software

that is published by the USA government.  Under

\href{http://www.law.cornell.edu/uscode/text/17/105}{17 USC 101 \S~105}, all

works published by the USA Government are not copyrightable in the USA.

\subsection{Why Copyright Free Software?}

If simply disclaiming copyright on software yields Free Software, then it

stands to reason that putting software into the public domain is the

easiest and most straightforward way to produce Free Software. Indeed,

some major Free Software projects have chosen this method for making their

software Free. However, most of the Free Software in existence \emph{is}

copyrighted. In most cases (particularly in those of FSF and the GNU

Project), this was done due to very careful planning.

Software released into the public domain does grant freedom to those users

who receive the standard versions on which the original author disclaimed

copyright. However, since the work is not copyrighted, any nontrivial

modification made to the work is fully copyrightable.

Free Software released into the public domain initially is Free, and

perhaps some who modify the software choose to place their work into the

public domain as well. However, over time, some entities will choose to

proprietarize their modified versions. The public domain body of software

feeds the proprietary software. The public commons disappears, because

fewer and fewer entities have an incentive to contribute back to the

commons. They know that any of their competitors can proprietarize their

enhancements. Over time, almost no interesting work is left in the public

domain, because nearly all new work is done by proprietarization.

A legal mechanism is needed to redress this problem. FSF was in fact

originally created primarily as a legal entity to defend software freedom,

and that work of defending software freedom is a substantial part of

its work today. Specifically because of this ``embrace, proprietarize and

extend'' cycle, FSF made a conscious choice to copyright its Free Software,

and then license it under ``copyleft'' terms. Many, including the

developers of the kernel named Linux, have chosen to follow this paradigm.

\label{copyleft-definition}

Copyleft,

which uses functional parts of copyright law to achieve an unusual result

(legal protection for free sharing) forms the core legal principle of these

licenses. It modifies, or ``hacks'' copyright law, which is usually employed to

strengthen the rights of authors or publishers, to strengthen instead the

rights of users.   %FIXME-URGENT: end

Copyleft is a legal strategy and mechanism to defend, uphold and propagate software

freedom. The basic technique of copyleft is as follows: copyright the

software, license it under terms that give all the software freedoms, but

use the copyright law controls to ensure that all who receive a copy of

the software have equal rights and freedom. In essence, copyleft grants

freedom, but forbids others to forbid that freedom to anyone else along

the distribution and modification chains.

% FIXME-URGENT: integrate

This ``reciprocity'' or ``share and share alike'' rule protects both

developers, who avoid facing a ``proprietized'' competitor of their project,

and users, who can be sure that they will have all four basic freedoms not

only in the present version of the program they use, but in all its future

improved versions.

% FIXME-URGENT: integrate

The unit of copyright law is ``the work''. In that sense, the ``work''

referenced by the licenses is anything that can be copyrighted or will be

subject to the terms of copyright law. The GNU licenses exercise their scope

fully. Anything which is ``a work'' or a ``work based on a work'' licensed

under GPL is subject to its requirements, including the requirement of

complete and corresponding source code, unless it is specifically

excepted. This principle often causes theoretical or speculative dispute

among lawyers, because ``the work'' is not a unit of computer programming. In

order to determine whether a ``routine'' an ``object'', a ``function'', a

``library'' or any other unit of software is part of one ``work'' when combined

with other GPL’d code, we must ask a question that copyright law will not

directly answer in the same technical terms.

The key here is that the GNU GPL licenses mean to ``plow fence row to fence

row'', covering every version of ``work based on the work'' recognized by local

copyright law, but no further.

%FIXME-URGENT: end

Copyleft is a general concept. Much like ideas for what a computer might

do must be \emph{implemented} by a program that actually does the job, so

too must copyleft be implemented in some concrete legal structure.

``Share and share alike'' is a phrase that is used often enough to explain the

concept behind copyleft, but to actually make it work in the real world, a

true implementation in legal text must exist. The GPL is the primary

implementation of copyleft in copyright licensing language.

\subsection{Software and Non-Copyright Legal Regimes}

\label{software-and-non-copyright}

The use, modification and distribution of software, like many endeavors,

simultaneously interacts with multiple different legal regimes.  As was noted

early via footnotes, copyright is merely the \textit{most common way} to

restrict users' rights to copy, share, modify and/or redistribute software.

However, proprietary software licenses typically use every mechanism

available to subjugate users.  For example:

\begin{itemize}

\item Unfortunately, despite much effort by many in the software freedom

  community to end patents that read on software (i.e., patents on

  computational ideas), they still ultimately exist.  As such, a software

  program might otherwise be seemly unrestricted, but a patent might read on

  the software and ruin everything for its users.\footnote{See

  \S\S~\ref{gpl-implied-patent-grant},~\ref{GPLv2s7},~\ref{GPLv3s11} for more

  discussion on how the patent system interacts with copyleft, and read

  Richard M.~Stallman's essay,

  \href{http://www.wired.com/opinion/2012/11/richard-stallman-software-patents/}{\textit{Let's

      Limit the Effect of Software Patents, Since We Can't Eliminate Them}}

  for more information on the problems these patents present to society.}

\item Digital Restrictions Management (usually called \defn{DRM}) is often

  used to impose technological restrictions on users' ability to exercise

  software freedom that they might otherwise be granted\footnote{See

    \S~\ref{GPLv3-drm} for more information on how GPL deals with this issue.}.

  The simplest (and perhaps oldest) form of DRM, of course, is separating

  software source code (read by humans), from their compiled binaries (read

  only by computers).  Furthermore,

  \href{http://www.law.cornell.edu/uscode/text/17/1201}{17 USC~\S1201} often

  prohibits users legally from circumventing some of these DRM systems.

\item Most EULAs also include a contractual agreement that bind users further

  by forcing them to agree to a contractual, prohibitive software license

  before ever even using the software.

\end{itemize}

Thus, most proprietary software restricts users via multiple interlocking

legal and technological means.  Any license that truly respect the software

freedom of all users must not only grant appropriate copyright permissions,

but also \textit{prevent} restrictions from other legal and technological

means like those listed above.

\subsection{Non-USA Copyright Regimes}

\label{non-usa-copyright}

Generally speaking, copyright law operates similarly enough in countries that

have signed the Berne Convention on Copyright, and software freedom licenses

have generally taken advantage of this international standardization of

copyright law.  However, copyright law does differ from country to country,

and commonly, software freedom licenses like the GPL must be considered under the

copyright law in the jurisdiction where any licensing dispute occurs.

Those who are most familiar with the USA's system of copyright often are

surprised to learn that there are certain copyright controls that cannot be

waived nor disclaimed.  Specifically, many copyright regimes outside the USA

recognize a concept of moral rights of authors.  Typically, moral rights are

fully compatible with respecting software freedom, as they are usually

centered around controls that software freedom licenses generally respect,

such as the right of an authors to require proper attribution for their work.

\section{A Community of Equality}

The previous section described the principles of software freedom, a brief

introduction to mechanisms that typically block these freedoms, and the

simplest ways that copyright holders might grant those freedoms to their

users for their copyrighted works of software.  The previous section also

introduced the idea of \textit{copyleft}: a licensing mechanism to use

copyright to not only grant software freedom to users, but also to uphold

those rights against those who might seek to curtail them.

Copyleft, as defined in \S~\ref{copyleft-definition}, is a general term for this

mechanism.  The remainder of this text will discuss details of various

real-world implementations of copyleft -- most notably, the GPL\@.

This discussion begins first with some general explanation of what the GPL is

able to do in software development communities.  After that brief discussion

in this section, deeper discussion of how GPL accomplishes this in practice

follows in the next chapter.

Simply put, though, the GPL ultimately creates a community of equality for

both business and noncommercial users.

\subsection{The Noncommercial Community}

A GPL'd code base becomes a center of a vibrant development and user

community.  Traditionally, volunteers, operating noncommercially out of

keen interest or ``scratch an itch'' motivations, produce initial versions

of a GPL'd system.  Because of the efficient distribution channels of the

Internet, any useful GPL'd system is adopted quickly by noncommercial

users.

Fundamentally, the early release and quick distribution of the software

gives birth to a thriving noncommercial community.  Users and developers

begin sharing bug reports and bug fixes across a shared intellectual

commons.  Users can trust the developers, because they know that if the

developers fail to address their needs or abandon the project, the GPL

ensures that someone else has the right to pick up development.

Developers know that the users cannot redistribute their software without

passing along the rights granted by the GPL, so they are assured that every

one of their users is treated equally.

Because of the symmetry and fairness inherent in GPL'd distribution,

nearly every GPL'd package in existence has a vibrant noncommercial user

and developer base.

\subsection{The Commercial Community}

By the same token, nearly all established GPL'd software systems have a

vibrant commercial community.  Nearly every GPL'd system that has gained

wide adoption from noncommercial users and developers eventually begins

to fuel a commercial system around that software.

For example, consider the Samba file server system that allows Unix-like

systems (including GNU/Linux) to serve files to Microsoft Windows systems.

Two graduate students originally developed Samba in their spare time and

it was deployed noncommercially in academic environments\footnote{See

  \href{http://turtle.ee.ncku.edu.tw/docs/samba/history}{Andrew Tridgell's

    ``A bit of history and a bit of fun''}}.  However, very

soon for-profit companies discovered that the software could work for them

as well, and their system administrators began to use it in place of

Microsoft Windows NT file-servers.  This served to lower the cost of

running such servers by orders of magnitude. There was suddenly room in

Windows file-server budgets to hire contractors to improve Samba.  Some of

the first people hired to do such work were those same two graduate

students who originally developed the software.

The noncommercial users, however, were not concerned when these two

fellows began collecting paychecks off of their GPL'd work.  They knew

that because of the nature of the GPL that improvements that were

distributed in the commercial environment could easily be folded back into

the standard version.  Companies are not permitted to proprietarize

Samba, so the noncommercial users, and even other commercial users are

safe in the knowledge that the software freedom ensured by the GPL will remain

protected.

Commercial developers also work in concert with noncommercial

developers.  Those two now-long-since graduated students continue to

contribute to Samba altruistically, but also get paid work doing it.

  You may not copy, modify, sublicense, link with, or distribute the

  library except as expressly provided under this License. Any attempt

  otherwise to copy, modify, sublicense, link with, or distribute the

  library is void, and will automatically terminate your rights under this

  License. However, parties who have received copies, or rights, from you

  under this License will not have their licenses terminated so long as

  such parties remain in full compliance.

\item  

  You are not required to accept this License, since you have not signed

  it. However, nothing else grants you permission to modify or distribute

  the library or its derivative works. These actions are prohibited by

  law if you do not accept this License. Therefore, by modifying or

  distributing the library (or any work based on the library), you

  indicate your acceptance of this License to do so, and all its terms and

  conditions for copying, distributing or modifying the library or works

  based on it.

\item

  Each time you redistribute the library (or any work based on the

  library), the recipient automatically receives a license from the

  original licensor to copy, distribute, link with or modify the library

  subject to these terms and conditions. You may not impose any further

  restrictions on the recipients' exercise of the rights granted herein.

  You are not responsible for enforcing compliance by third parties with

  this License.

\item

  If, as a consequence of a court judgment or allegation of patent

  infringement or for any other reason (not limited to patent issues),

  conditions are imposed on you (whether by court order, agreement or

  otherwise) that contradict the conditions of this License, they do not

  excuse you from the conditions of this License. If you cannot

  distribute so as to satisfy simultaneously your obligations under this

  License and any other pertinent obligations, then as a consequence you

  may not distribute the library at all. For example, if a patent license

  would not permit royalty-free redistribution of the library by all those

  who receive copies directly or indirectly through you, then the only way

  you could satisfy both it and this License would be to refrain entirely

  from distribution of the library.

  If any portion of this section is held invalid or unenforceable under

  any particular circumstance, the balance of the section is intended to

  apply, and the section as a whole is intended to apply in other

  circumstances.

  It is not the purpose of this section to induce you to infringe any

  patents or other property right claims or to contest validity of any

  such claims; this section has the sole purpose of protecting the

  integrity of the Free Software distribution system which is implemented

  by public license practices. Many people have made generous

  contributions to the wide range of software distributed through that

  system in reliance on consistent application of that system; it is up to

  the author/donor to decide if he or she is willing to distribute

  software through any other system and a licensee cannot impose that

  choice.

  This section is intended to make thoroughly clear what is believed to be

  a consequence of the rest of this License.

% \pagebreak[4]

\item 

  If the distribution and/or use of the library is restricted in certain

  countries either by patents or by copyrighted interfaces, the original

  copyright holder who places the library under this License may add an

  explicit geographical distribution limitation excluding those countries,

  so that distribution is permitted only in or among countries not thus

  excluded. In such case, this License incorporates the limitation as if

  written in the body of this License.

\item 

  The Free Software Foundation may publish revised and/or new versions of

  the Lesser General Public License from time to time. Such new versions

  will be similar in spirit to the present version, but may differ in

  detail to address new problems or concerns.

  Each version is given a distinguishing version number. If the library

  specifies a version number of this License which applies to it and ``any

  later version,'' you have the option of following the terms and

  conditions either of that version or of any later version published by

  the Free Software Foundation. If the library does not specify a license

  version number, you may choose any version ever published by the Free

  Software Foundation.

\item

  If you wish to incorporate parts of the library into other Free programs

  whose distribution conditions are incompatible with these, write to the

  author to ask for permission. For software which is copyrighted by the

  Free Software Foundation, write to the Free Software Foundation; we

  sometimes make exceptions for this. Our decision will be guided by the

  two goals of preserving the Free status of all derivatives of our Free

  software and of promoting the sharing and reuse of software generally.

\begin{center}

{\Large\sc

No Warranty

}

\end{center}

\item

{\sc Because the library is licensed free of charge, there is no

warranty for the library, to the extent permitted by applicable law.

Except when otherwise stated in writing the copyright holders and/or

other parties provide the library ``as is'' without warranty of any

kind, either expressed or implied, including, but not limited to, the

implied warranties of merchantability and fitness for a particular

purpose. The entire risk as to the quality and performance of the

library is with you. should the library prove defective, you assume

the cost of all necessary servicing, repair or correction.}

% \pagebreak[4]

\item

{\sc In no event unless required by applicable law or agreed to in writing

  will any copyright holder, or any other party who may modify and/or

  redistribute the library as permitted above, be liable to you for

  damages, including any general, special, incidental or consequential

  damages arising out of the use or inability to use the library

  (including but not limited to loss of data or data being rendered

  inaccurate or losses sustained by you or third parties or a failure of

  the library to operate with any other software), even if such holder or

  other party has been advised of the possibility of such damages.}

\end{enumerate}

\begin{center}

{\Large\sc End of Terms and Conditions}

\end{center}

\vfill

\pagebreak[4]

\section*{How to Apply These Terms to Your New Libraries}

If you develop a new library, and you want it to be of the greatest

possible use to the public, we recommend making it Free Software that

everyone can redistribute and change. You can do so by permitting

redistribution under these terms (or, alternatively, under the terms of

the ordinary General Public License).

To apply these terms, attach the following notices to the library. It is

safest to attach them to the start of each source file to most effectively

convey the exclusion of warranty; and each file should have at least the

``copyright'' line and a pointer to where the full notice is found.

\begin{quote}

one line to give the library's name and a brief idea of what it does. \\

Copyright (C) year  name of author \\

This library is Free Software; you can redistribute it and/or modify it

under the terms of the GNU Lesser General Public License as published by

the Free Software Foundation; either version 2.1 of the License, or (at

your option) any later version.

This library is distributed in the hope that it will be useful, but

WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY

or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public

License for more details.

You should have received a copy of the GNU Lesser General Public License

along with this library; if not, write to the Free Software Foundation,

Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

\end{quote}

Also add information on how to contact you by electronic and paper mail.

You should also get your employer (if you work as a programmer) or your

school, if any, to sign a ``copyright disclaimer'' for the library, if

necessary. Here is a sample; alter the names:

\begin{quote}

Yoyodyne, Inc., hereby disclaims all copyright interest in the program \\

`Gnomovision' (which makes passes at compilers) written by James Hacker. \\

signature of Ty Coon, 1 April 1990 \\

Ty Coon, President of Vice

\end{quote}

\chapter{The GNU General Public License, version 3}

\begin{center}

{\parindent 0in

Version 3, 29 June 2007

Copyright \copyright\  2007 Free Software Foundation, Inc. \texttt{http://fsf.org/}

\bigskip

Everyone is permitted to copy and distribute verbatim copies of this

license document, but changing it is not allowed.}

\end{center}

\begin{center}

{\bf\large Preamble}

\end{center}

The GNU General Public License is a free, copyleft license for

software and other kinds of works.

The licenses for most software and other practical works are designed

to take away your freedom to share and change the works.  By contrast,

the GNU General Public License is intended to guarantee your freedom to

share and change all versions of a program--to make sure it remains free

software for all its users.  We, the Free Software Foundation, use the

GNU General Public License for most of our software; it applies also to

any other work released this way by its authors.  You can apply it to

your programs, too.

When we speak of free software, we are referring to freedom, not

price.  Our General Public Licenses are designed to make sure that you

have the freedom to distribute copies of free software (and charge for

them if you wish), that you receive source code or can get it if you

want it, that you can change the software or use pieces of it in new

free programs, and that you know you can do these things.

To protect your rights, we need to prevent others from denying you

these rights or asking you to surrender the rights.  Therefore, you have

certain responsibilities if you distribute copies of the software, or if

you modify it: responsibilities to respect the freedom of others.

For example, if you distribute copies of such a program, whether

gratis or for a fee, you must pass on to the recipients the same

freedoms that you received.  You must make sure that they, too, receive

or can get the source code.  And you must show them these terms so they

know their rights.

Developers that use the GNU GPL protect your rights with two steps:

(1) assert copyright on the software, and (2) offer you this License

giving you legal permission to copy, distribute and/or modify it.

For the developers' and authors' protection, the GPL clearly explains

that there is no warranty for this free software.  For both users' and

authors' sake, the GPL requires that modified versions be marked as

changed, so that their problems will not be attributed erroneously to

authors of previous versions.

Some devices are designed to deny users access to install or run

modified versions of the software inside them, although the manufacturer

can do so.  This is fundamentally incompatible with the aim of

protecting users' freedom to change the software.  The systematic

pattern of such abuse occurs in the area of products for individuals to

use, which is precisely where it is most unacceptable.  Therefore, we

have designed this version of the GPL to prohibit the practice for those

products.  If such problems arise substantially in other domains, we

stand ready to extend this provision to those domains in future versions

of the GPL, as needed to protect the freedom of users.

Finally, every program is threatened constantly by software patents.

States should not allow patents to restrict development and use of

software on general-purpose computers, but in those that do, we wish to

avoid the special danger that patents applied to a free program could

make it effectively proprietary.  To prevent this, the GPL assures that

patents cannot be used to render the program non-free.

The precise terms and conditions for copying, distribution and

modification follow.

\begin{center}

{\Large \sc Terms and Conditions}

\end{center}

\begin{enumerate}

\addtocounter{enumi}{-1}

\item Definitions.

``This License'' refers to version 3 of the GNU General Public License.

``Copyright'' also means copyright-like laws that apply to other kinds of

works, such as semiconductor masks.

``The Program'' refers to any copyrightable work licensed under this

License.  Each licensee is addressed as ``you''.  ``Licensees'' and

``recipients'' may be individuals or organizations.

To ``modify'' a work means to copy from or adapt all or part of the work

in a fashion requiring copyright permission, other than the making of an

exact copy.  The resulting work is called a ``modified version'' of the

earlier work or a work ``based on'' the earlier work.

A ``covered work'' means either the unmodified Program or a work based

on the Program.

To ``propagate'' a work means to do anything with it that, without

permission, would make you directly or secondarily liable for

infringement under applicable copyright law, except executing it on a

computer or modifying a private copy.  Propagation includes copying,

distribution (with or without modification), making available to the

public, and in some countries other activities as well.

To ``convey'' a work means any kind of propagation that enables other

parties to make or receive copies.  Mere interaction with a user through

a computer network, with no transfer of a copy, is not conveying.

An interactive user interface displays ``Appropriate Legal Notices''

to the extent that it includes a convenient and prominently visible

feature that (1) displays an appropriate copyright notice, and (2)

tells the user that there is no warranty for the work (except to the

extent that warranties are provided), that licensees may convey the

work under this License, and how to view a copy of this License.  If

the interface presents a list of user commands or options, such as a

menu, a prominent item in the list meets this criterion.

\item Source Code.

The ``source code'' for a work means the preferred form of the work

for making modifications to it.  ``Object code'' means any non-source

form of a work.

A ``Standard Interface'' means an interface that either is an official

standard defined by a recognized standards body, or, in the case of

interfaces specified for a particular programming language, one that

is widely used among developers working in that language.

The ``System Libraries'' of an executable work include anything, other

than the work as a whole, that (a) is included in the normal form of

packaging a Major Component, but which is not part of that Major

Component, and (b) serves only to enable use of the work with that

Major Component, or to implement a Standard Interface for which an

implementation is available to the public in source code form.  A

``Major Component'', in this context, means a major essential component

(kernel, window system, and so on) of the specific operating system

(if any) on which the executable work runs, or a compiler used to

produce the work, or an object code interpreter used to run it.

The ``Corresponding Source'' for a work in object code form means all

the source code needed to generate, install, and (for an executable

work) run the object code and to modify the work, including scripts to

control those activities.  However, it does not include the work's

System Libraries, or general-purpose tools or generally available free

programs which are used unmodified in performing those activities but

which are not part of the work.  For example, Corresponding Source

includes interface definition files associated with source files for

the work, and the source code for shared libraries and dynamically

linked subprograms that the work is specifically designed to require,

such as by intimate data communication or control flow between those

subprograms and other parts of the work.

The Corresponding Source need not include anything that users

can regenerate automatically from other parts of the Corresponding

Source.

The Corresponding Source for a work in source code form is that

same work.

\item Basic Permissions.

All rights granted under this License are granted for the term of

copyright on the Program, and are irrevocable provided the stated

conditions are met.  This License explicitly affirms your unlimited

permission to run the unmodified Program.  The output from running a

covered work is covered by this License only if the output, given its

content, constitutes a covered work.  This License acknowledges your

rights of fair use or other equivalent, as provided by copyright law.

You may make, run and propagate covered works that you do not

convey, without conditions so long as your license otherwise remains

in force.  You may convey covered works to others for the sole purpose

of having them make modifications exclusively for you, or provide you

with facilities for running those works, provided that you comply with

the terms of this License in conveying all material for which you do

not control copyright.  Those thus making or running the covered works

for you must do so exclusively on your behalf, under your direction

and control, on terms that prohibit them from making any copies of

your copyrighted material outside their relationship with you.

Conveying under any other circumstances is permitted solely under

the conditions stated below.  Sublicensing is not allowed; section 10