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<chapter label="20" id="GPL">

<title>GNU General Public License</title>

<programlisting>
                         GNU GENERAL PUBLIC LICENSE
     
                            Version 2, June 1991
     
     Copyright (C) 1989, 1991 Free Software Foundation, Inc.
     
     59 Temple Place, Suite 330, Boston, MA
     
     02111-1307 USA
     
     Everyone is permitted to copy and distribute verbatim copies of
     this license document, but changing it is not allowed.
     
                                  Preamble
     
     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 follow.
     
                         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 conditions:
     
     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 it.
     
     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 licensor 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 License.
     
     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.
     
     NO WARRANTY
     
     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 which 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; and each file should have at
     least the "copyright" line and a pointer to where the full notice
     is found.
     
     &lt;one line to give the program's name and a brief idea of what it
     does.>
     
     Copyright (C) &lt;year> &lt;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 version.
     
     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., 59 Temple Place, Suite 330, Boston, MA 02111-1307
     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) year name of author
     Gnomovision comes 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
     details.
     
     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 program.
     
     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.
     
     &lt;signature of Ty Coon>, 1 April 1989 Ty Coon, President of Vice
     
     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.
</programlisting>

</chapter>
