为何使用了png图替代jpeg

（简体中文参考版） 1991年6月，第二版
（原文出处: http://www.gnu.org/copyleft/gpl.html）
著作权所有 (C) 1989，1991 Free Software Foundation, Inc.
59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
允许每个人复制和散布本授权文件的完整副本，但不允许对它进行任何修改。

声明

　　This is an unofficial translation of the GNU General Public License into Chinese. It was not published by the Free Software Foundation, and does not legally state the distribution terms for software that uses the GNU GPL--only the original English text of the GNU GPL does that. However, we hope that this translation will help Chinese speakers understand the GNU GPL better.

　　这是一份 GNU 通用公共授权非正式的中文翻译。它并非由自由软件基金会所发表，亦非使用 GNU 通用公共授权的软件的法定散布条款——只有 GNU 通用公共授权英文原文的版本始具有此等效力。然而，我们希望这份翻译能帮助中文的使用者更了解 GNU 通用公共授权。

前言

　　大多数软件授权声明是设计用以剥夺您分享与修改软件的自由。相反地，GNU通用公共授权力图保证您分享与修改自由软件的自由—确保软件对所有的 使用者而言都是自由的。通用公共授权适用于大多数自由软件基金会的软件，以及任何作者指定使用本授权的其他软件。（有些自由软件基金会的软件，则适用 GNU函数库通用公共授权规定。）您也可以让您的软件适用本授权规定。

　　当我们在谈论自由软件时，我们所指的是自由，而非价格。我们的通用公共授权系设计用以确保使您保有散布自由软件重制物的自由（以及您可以决定此 一服务是否收费），确保您能收到源码或者在您需要时便能得到它，确保您能变更软件或将它的一部分用于新的自由软件；并且确保您知道您可以从事上述的事情。

　　为了保障您的权利，我们需要作出限制：禁止任何人否认您上述的权利，或者要求您放弃这些权利。如果您散布软件的副本，或者对之加以修改，这些限制就转化成为您的责任。

　　例如，假如您散布此类程序的副本，无论是免费或收取费用，您必须将您所享有的一切权利交付收受者。您也必须确保他们能收到或得到源码。而且您必须向他们展示这些条款的内容，使他们知悉他们所享有的权利。

　　我们采取两项措施来保护您的权利：(1)以著作权保护软件，以及(2)提供您本授权，赋与您复制、散布及／或修改软件的法律许可。

　　同时，为了保护作者与我们（按：指自由软件基金会），我们希望确定每个人都明了，自由软件是没有担保责任的。如果软件被他人修改并加以传递，我们需要其收受者知道，他们所得到的并非原软件，因此由他人所引出的任何问题对原作者的声誉将不会有任何的影响。

　　最后，所有自由软件不断地受到软件专利的威胁。我们希望能避免自由软件的再散布者以个人名义取得专利授权而使程序专有化的风险。为了防止上述的情事发生，我们在此明确声明：任何专利都必须为了每个人的自由使用而核准，否则就不应授与专利。

　　以下是有关复制、散布及修改的明确条款及条件。

复制、散布与修改的条款与条件

　　0.凡著作权人在其程序或其他著作中声明，该程序或著作得在通用公共授权条款下散布，本授权对其均有适用。以下所称的“本程序”，系指任何一种 适用通用公共授权的程序或著作；“基于本程序所生的著作”，则指本程序或任何基于著作权法所产生的衍生著作，换言之，系指包含本程序全部或一部的著作，不 论是完整的或经过修改的程序，以及（或）翻译成其他语言的程序（以下“修改”一词包括但不限于翻译行为在内）。被授权人则称为“您”。

　　本授权不适用于复制、散布与修改以外的行为；这些行为不在本授权范围内。执行本程序的行为并不受限制，而本程序的输出只有在其内容构成基于本程 序所生的著作（而非只是因为执行本程序所造成）时，始受本授权拘束。至于程序的输出内容是否构成本程序的衍生著作，则取决于本程序的具体用途。

　　1.您可以对所收受的本程序源码，无论以何种媒介，复制与散布其完整的重制物，然而您必须符合以下要件：以显著及适当的方式在每一份重制物上发 布适当的著作权标示及无担保声明；维持所有有关本授权以及无担保声明的原貌；并将本授权的副本连同本程序一并交付予其他任一位本程序的收受者。

　　您可以对让与重制物的实际行为请求一定的费用，您也可以自由决定是否提供担保以作为对价的交换。

　　2.您可以修改本程序的一个或数个重制物或者本程序的任何部份，以此形成基于本程序所生的著作，并依前述第一条规定，复制与散布此一修改过的程序或著作，但您必须符合以下要件：

　　(a)您必须在所修改的文件上附加显著的标示，叙明您修改过这些文件，以及修改日期。
　　(b)您必须就您所散布或发行的著作，无论是包含本程序全部或一部的著作，或者是自本程序或其任何部份所衍生的著作，整体授权所有第三人依本授权规定使用，且不得因此项授权行为而收取任何费用。
　　(c)若经过修改的程序在执行时通常以互动方式读取命令时，您必须在最常被使用的方式下，于开始进入这种互动式使用时，列印或展示以下宣告：适当的著 作权标示及无担保声明（或者声明您提供担保）、使用者可以依这些条件再散布此程序，以及告知使用者如何浏览本授权的副本。（例外：若本程序本身系以互动的 方式执行，然而通常却不会列印该宣告时，则您基于本程序所生的著作便无需列印该宣告。）
　　这些要求对修改过的著作是整体适用的。倘著作中可识别的一部份并非衍生自本程序，并且可以合理地认为是一独立的、个别的著作，则当您将其作为个别著作 加以散布时，本授权及其条款将不适用于该部分。然而当您将上述部分，作为基于本程序所生著作的一部而散布时，整个著作的散布必须符合本授权条款的规定，而 本授权对于其他被授权人所为的许可及于著作整体。
　　因此，本条规定的意图不在于主张或剥夺您对于完全由您所完成著作的权利；应该说，本条规定意在行使对基于程序所生的之衍生著作或集合著作散布行为的控制权。
　　此外，非基于本程序所生的其他著作与本程序（或基于本程序所生的著作）在同一储存或散布的媒介上的单纯聚集行为，并不会使该著作因此受本授权条款拘束。

　　3.您可以依前述第一、二条规定，复制与散布本程序（或第二条所述基于本程序所产生的著作）的目的码或可执行形式，但您必须符合以下要件：
　　(a)附上完整、相对应的机器可判读源码，而这些源码必须依前述第一、二条规定在经常用以作为软件交换的媒介物上散布；或
　　(b)附上至少三年有效的书面报价文件，提供任何第三人在支付不超过实际散布源码所需成本的费用下，取得相同源码的完整机器可读重制物，并依前述第一、二条规定在经常用以作为软件交换的媒介物上散布该重制物；或
　　(c)附上您所收受有关散布相同源码的报价信息。（本项选择仅在非营利散布、且仅在您依前述b项方式自该书面报价文件收受程序目的码或可执行形式时，始有适用。）
　　 著作的源码，是指对著作进行修改时适用的形式。对于一个可执行的著作而言，完整的源码是指著作中所包含所有模组的全部源码，加上相关接口的定义档，还加上用以控制该著作编绎与安装的描述。然而，特别的例外情况是，所散布的源码并不需包含任何通常会随着所执行作业系统的主要组成部分（编译器、核心等等）而散 布的软件（无论以源码或二进位格式），除非该部分本身即附加在可执行程序中。
　　若可执行码或目的码的散布方式，是以指定的地点提供存取位置供人复制，则提供可自相同地点复制源码的使用机会，视同对于源码的散布，然而第三人并不因此而负有将目的码连同源码一并复制的义务。

　　4.除本授权所明示的方式外，您不得对本程序加以复制、修改、再授权或散布。任何试图以其他方式进行复制、修改、再授权或者散布本程序的行为均为无效，并且将自动终止您基于本授权所得享有的权利。然而，依本授权规定自您手中收受重制物或权利之人，只要遵守本授权规定，他们所获得的授权并不会因此 终止。

　　5.因为您并未在本授权上签名，所以您无须接受本授权。然而，除此之外您别无其他修改或散布本程序或其衍生著作的授权许可。若您不接受本授权，则这些行为在法律上都是被禁止的。因此，藉由对本程序（或任何基于本程序所生的著作）的修改或散布行为，您表示了对于本授权的接受，以及接受所有关于复 制、散布或修改本程序或基于本程序所生著作的条款与条件。

　　6.每当您再散布本程序（或任何基于本程序所生的著作）时，收受者即自动获得原授权人所授予依本授权条款与条件复制、散布或修改本程序的权利。您不得就本授权所赋予收受者行使的权利附加任何进一步的限制。您对于第三人是否履行本授权一事，无须负责。

　　7.若法院判决、专利侵权主张或者其他任何理由（不限于专利争议）的结果，使得加诸于您的条件（无论是由法院命令、协议或其他方式造成）与本授 权规定有所冲突，他们并不免除您对于本授权规定的遵守。若您无法同时符合依本授权所生义务及其他相关义务而进行散布，那么其结果便是您不得散布该程序。例 如，若专利授权不允许直接或间接透过您而取得重制物之人，以免付权利金的方式再散布该程序时，您唯一能同时满足该义务及本授权的方式就是彻底避免进行该程序的散布。

　　若本条任一部份在特殊情况下被认定无效或无法执行时，本条其余部分仍应适用，且本条全部于其他情况下仍应适用。

　　本条的目的并不在诱使您侵害专利或其他财产权的权利主张，或就此类主张的有效性加以争执；本条的唯一目的，是在保障藉由公共授权惯例所执行自由 软件散布系统的完整性。许多人信赖该系统一贯使用的应用程序，而对经由此系统散布的大量软件有相当多的贡献；作者／贡献者有权决定他或她是否希望经由其他 的系统散布软件，而被授权人则无该种选择权。

　　本条的用意在于将本授权其他不确定的部分彻底解释清楚。

　　 8.若因为专利或享有著作权保护的接口问题，而使得本程序的散布与／或使用局限于某些国家时，则将本程序置于本授权规范之下的原著作权人得增列明确的散布 地区限制条款，将该等国家排除在外，而使散布的许可只限在未受排除的国家之内或之中。在该等情况下，该限制条款如同以书面方式订定于本授权内容中，而成为 本授权的条款。

　　9.自由软件基金会得随时发表通用公共授权的修正版与／或新版本。新版本在精神上将近似于目前的版本，然而在细节上或所不同以因应新的问题或状况。

　　每一个版本都有个别的版本号码。若本程序指定有授权版本号码，表示其适用该版本或是“任何新版本”时，您得选择遵循该版本或任何由自由软件基金会日后所发表新版本的条款与条件。若本程序并未指定授权版本号码时，您便得选择任一自由软件基金会所发表的版本。

　　 10.若您想将部分本程序纳入其他自由程序，而其散布的条件有所不同时，请写信取得作者的许可。若为自由软件基金会享有著作权的软件，请写信至自由软件基 金会；我们有时会以例外方式予以处理。我们的决定取决于两项目标：确保我们自由软件的所有衍生著作均维持在自由的状态，并广泛地促进软件的分享与再利用。

无担保声明

　　11.由于本程序系无偿授权，因此在法律许可范围内，本授权对本程序并不负担保责任。非经书面声明，著作权人与／或其他提供程序之人，无论明示 或默示，均系依“现况”提供本程序而并无任何形式的担保责任，其包括但不限于，就适售性以及特定目的的适用性为默示性担保。有关本程序品质与效能的全部风 险悉由您承担。如本程序被证明有瑕疵，您应承担所有服务、修复或改正的费用。
　　 12.非经法律要求或书面同意，任何著作权人或任何可能依前述方式修改与／或散布本程序者，对于您因为使用或不能使用本程序所造成的一般性、特殊性、意外 性或间接性损失，不负任何责任（包括但不限于，资料损失，资料执行不精确，或应由您或第三人承担的损失，或本程序无法与其他程序运作等），即便前述的著作 权人或其他人已被告知该等损失的可能性时，亦同。

　　 条文结束。

您的新程序该如何采用这些条款？

　　如果您开发了一个新程序，并且希望能够让它尽可能地被大众使用，达成此目的的最好方式就是让它成为自由软件，任何人依这些条款规定都能就该软件再为散布及修改。

　　为了做到这一点，请将以下声明附加到程序上。最安全的作法，是将声明放在每份源码文件的起始处，以有效传达无担保责任的信息；且每份文件至少应有“著作权”列以及本份声明全文位置的提示。

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.

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.

one line to give the program's name and an idea of what it does.
Copyright (C) yyyy  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.

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 Lesser General Public License instead of this License.