UNIX Unleashed, Internet Edition
- A -
The GNU General Public License
Linux is licensed under the GNU General Public License (the GPL or copyleft),
which is reproduced here to clear up some of the confusion about Linux's copyright
Linux is not shareware, nor is it in the public domain. The bulk of the Linux
kernel has been copyrighted since 1993 by Linus Torvalds, and other software and
parts of the kernel are copyrighted by their authors. Thus, Linux is copyrighted.
Everyone is permitted to copy and distribute verbatim copies of this license document,
but changing it is not allowed.
However, you may redistribute it under the terms of the GPL, which follows.
GNU GENERAL PUBLIC LICENSE, Version 2, June 1991
Copyright 1989, 1991
Free Software Foundation, Inc.
675 Mass Ave.
Cambridge, MA 02139
Everyone is permitted to copy and distribute verbatim copies of this license
document, but changing it is not allowed.
The licenses for most software are designed to take away your freedom to share
and change it. By contrast, the GNU General Public License is intended to guarantee
your freedom to share and change free software--to make sure the software is free
for all its users. This General Public License applies to most of the Free Software
Foundation's software and to any other program whose authors commit to using it.
(Some other Free Software Foundation software is covered by the GNU Library General
Public License instead.)
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 this service 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 make restrictions that forbid anyone to
deny you these rights or to ask you to surrender the rights.
These restrictions translate to certain responsibilities for you if you distribute
copies of the software, or if you modify it.
For example, if you distribute copies of such a program, whether gratis or
for a fee, you must give the recipients all the rights that you have. 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.
We protect your rights with two steps:
- 1. Copyright the software, and
2. Offer you this license which gives you legal permission to copy, distribute
and/or modify the software.
Also, for each author's protection and ours, we want to make certain that everyone
understands that there is no warranty for this free software. If the software is
modified by someone else and passed on, we want its recipients to know that what
they have is not the original, so that any problems introduced by others will not
reflect on the original authors' reputations.
Finally, any free program is threatened constantly by software patents. We
wish to avoid the danger that redistributors of a free program will individually
obtain patent licenses, in effect making the program proprietary. To prevent this,
we have made it clear that any patent must be licensed for everyone's free use or
not licensed at all.
The precise terms and conditions for copying, distribution, and modification
E.2. GNU General Public License: Terms and Conditions for
Copying, Distribution, and Modification
0. This License applies to any program or other work which contains a notice
placed by the copyright holder saying it may be distributed under the terms of this
General Public License. The "Program," below, refers to any such program
or work, and "a work based on the Program" means either the Program or
any derivative work under copyright law: that is to say, a work containing the Program
or a portion of it, either verbatim or with modifications and/or translated into
another language. (Hereinafter, translation is included without limitation in the
term "modification.") Each licensee is addressed as "you."
Activities other than copying, distribution, and modification are not covered
by this License; they are outside its scope. The act of running the Program is not
restricted, and the output from the Program is covered only if its contents constitute
a work based on the Program (independent of having been made by running the Program).
Whether that is true depends on what the Program does.
- 1. You may copy and distribute verbatim copies of the Program's source code
as you receive it, in any medium, provided that you conspicuously and appropriately
publish on each copy an appropriate copyright notice and disclaimer of warranty;
keep intact all the notices that refer to this License and to the absence of any
warranty; and give any other recipients of the Program a copy of this License along
with the Program.
You may charge a fee for the physical act of transferring a copy, and you may
at your option offer warranty protection in exchange for a fee.
2. You may modify your copy or copies of the Program or any portion of it, thus
forming a work based on the Program, and copy and distribute such modifications or
work under the terms of Section 1 above, provided that you also meet all of these
- a. You must cause the modified files to carry prominent notices stating that
you changed the files and the date of any change.
b. You must cause any work that you distribute or publish, that in whole or in
part contains or is derived from the Program or any part thereof, to be licensed
as a whole at no charge to all third parties under the terms of this License.
c. If the modified program normally reads commands interactively when run, you
must cause it, when started running for such interactive use in the most ordinary
way, to print or display an announcement including an appropriate copyright notice
and a notice that there is no warranty (or else, saying that you provide a warranty)
and that users may redistribute the program under these conditions, and telling the
user how to view a copy of this License. (Exception: if the Program itself is interactive
but does not normally print such an announcement, your work based on the Program
is not required to print an announcement.)
These requirements apply to the modified work as a whole. If identifiable sections
of that work are not derived from the Program, and can be reasonably considered independent
and separate works in themselves, then this License, and its terms, do not apply
to those sections when you distribute them as separate works. But when you distribute
the same sections as part of a whole which is a work based on the Program, the distribution
of the whole must be on the terms of this License, whose permissions for other licensees
extend to the entire whole, and thus to each and every part regardless of who wrote
Thus, it is not the intent of this section to claim rights or contest your rights
to work written entirely by you; rather, the intent is to exercise the right to control
the distribution of derivative or collective works based on the Program.
In addition, mere aggregation of another work not based on the Program with the
Program (or with a work based on the Program) on a volume of a storage or distribution
medium does not bring the other work under the scope of this License.
3. You may copy and distribute the Program (or a work based on it, under Section
2) in object code or executable form under the terms of Sections 1 and 2 above, provided
that you also do one of the following:
- a. Accompany it with the complete corresponding machine-readable source code,
which must be distributed under the terms of Sections 1 and 2 above on a medium customarily
used for software interchange; or,
b. Accompany it with a written offer, valid for at least three years, to give
any third party, for a charge no more than your cost of physically performing source
distribution, a complete machine-readable copy of the corresponding source code,
to be distributed under the terms of Sections 1 and 2 above on a medium customarily
used for software interchange; or,
c. Accompany it with the information you received as to the offer to distribute
corresponding source code. (This alternative is allowed only for noncommercial distribution
and only if you received the program in object code or executable form with such
an offer, in accord with Subsection b above.)
The source code for a work means the preferred form of the work for making modifications
to it. For an executable work, complete source code means all the source code for
all modules it contains, plus any associated interface definition files, plus the
scripts used to control compilation and installation of the executable. However,
as a special exception, the source code distributed need not include anything that
is normally distributed (in either source or binary form) with the major components
(compiler, kernel, and so on) of the operating system on which the executable runs,
unless that component itself accompanies the executable.
If distribution of executable or object code is made by offering access to copy
from a designated place, then offering equivalent access to copy the source code
from the same place counts as distribution of the source code, even though third
parties are not compelled to copy the source along with the object code.
4. You may not copy, modify, sublicense, or distribute the Program except as expressly
provided under this License. Any attempt otherwise to copy, modify, sublicense, or
distribute the Program 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.
5. 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 Program or
its derivative works. These actions are prohibited by law if you do not accept this
License. Therefore, by modifying or distributing the Program (or any work based on
the Program), you indicate your acceptance of this License to do so, and all its
terms and conditions for copying, distributing, or modifying the Program or works
based on it.
6. Each time you redistribute the Program (or any work based on the Program),
the recipient automatically receives a license from the original licenser to copy,
distribute, or modify the Program 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 to this
7. 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 Program at all. For example, if a patent license would not permit royalty-free
redistribution of the Program 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 Program.
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.
8. If the distribution and/or use of the Program is restricted in certain countries
either by patents or by copyrighted interfaces, the original copyright holder who
places the Program 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.
9. The Free Software Foundation may publish revised and/or new versions of the
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 Program 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 Program
does not specify a version number of this License, you may choose any version ever
published by the Free Software Foundation.
10. If you wish to incorporate parts of the Program into other free programs whose
distribution conditions are different, 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.
- 11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR
THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED
IN WRITING, THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "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 PROGRAM IS WITH
YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING,
REPAIR, OR CORRECTION.
12. 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 PROGRAM 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 PROGRAM (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 PROGRAM
TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN
ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
END OF TERMS AND CONDITIONS
How to Apply These Terms to Your New Programs
If you develop a new program and you want it to be of the greatest possible use
to the public, the best way to achieve this is to make it free software that everyone
can redistribute and change under these terms.
To do so, attach the following notices to the program. It is safest to attach
them to the start of each source file to most effectively convey the exclusion of
warranty. Each file should have at least the "copyright" line and a pointer
to where the full notice is found:
Copyright (C) 19yy <name of author>
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License as published by the Free
Software Foundation; either version 2 of the License, or (at your option) any later
This program 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 General Public License for more details.
You should have received a copy of the GNU General Public License along with this
program; if not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge,
MA 02139, USA.
Also add information on how to contact you by electronic and paper mail.
If the program is interactive, make it output a short notice like this when it
starts in an interactive mode:
Gnomovision version 69, Copyright (C) 19yy name of author
with ABSOLUTELY NO WARRANTY; for details type ` show w'. This is free software,
and you are welcome to redistribute it under certain conditions; type ` show c' for
The hypothetical commands ` show w' and ` show
c' should show the appropriate parts of the General Public License. Of course,
the commands you use may be called something other than ` show w' and `
show c'; they could even be mouse-clicks or menu items--whatever suits your
You should also get your employer (if you work as a programmer) or your school,
if any, to sign a "copyright disclaimer" for the program, if necessary.
Here is a sample; alter the names:
Yoyodyne, Inc., hereby disclaims all copyright interest in the program `Gnomovision'
(which makes passes at compilers) written by James Hacker.
1 April 1989
Ty Coon, President of V.
This General Public License does not permit incorporating your program into proprietary
programs. If your program is a subroutine library, you may consider it more useful
to permit linking proprietary applications with the library. If this is what you
want to do, use the GNU Library General Public License instead of this License.
Macmillan Computer Publishing. All rights reserved.