The GNU Public License

only for RuBoard - do not distribute or recompile

PHP is licensed under either the GNU Public License (GPL) or the PHP license, according to the Web page at http://www.php.net/license.html. You can choose to distribute PHP under either license. I will cover PHP as distributed under the GPL.

What It Means

First, I must strongly state that I am not an attorney, and if you need a true legal opinion on this matter, you should consult one. My opinions as expressed in the following paragraphs are not legal opinions; they are my thoughts about what you can do under Public Domain rules and under the GNU Public License. The GNU Public license (GPL) is in plain language, and I am expressing my views as they come from reading the license in a plain-language sense. These opinions are only mine, and they might be wrong. Only courts of law can rule on the legal nuances of the GPL.

The GPL is included at the end of this book. It is an interesting license. It differs from Public Domain in several critical ways.

In general, Public Domain material is free for use. It is usually widely available. You can take Public Domain information and modify it. The changes you make to Public Domain material might or might not be part of the Public Domain. As author of the changes, it is generally up to you, along with legal counsel, to decide. In some cases you might not have to distribute your changes to public domain material.

Other implications to modifying Public Domain material could be worked out within the legal system. You should consult a licensed attorney before distributing Public Domain material, either modified or not. It is best to consult an attorney who specializes in this field.

The GNU Public License (GPL) is different. Under the GPL, you can take the code and modify it for any purpose, and you can transfer it to any entity.

The GPL says you can charge money for cost of the transfer of any software covered under the GPL. You must also allow the entity that purchases software covered under the GPL to obtain the source code. You can charge money for the transfer of this source code to that entity.

After you have transferred the software or source code, that entity is bound by the GPL. You have no control over what is done to the software or source code you have transferred. That entity can modify it and transfer the modified or unmodified software under the same rules you had to follow.

It also specifies that your changes to any material covered under the GPL are immediately covered under the GPL. You must give these changes to the person or entity that obtains your compiled software if it contained those changes, at their request.

A loophole is possible in the GPL concerning code placed under it. If you have private version 1.0 of code, and generate version 1.1, you can place version 1.1 under the GPL. It appears that you can then take version 1.0 of the code and improve it to private version 2.0. Private version 2.0 of your code is not under the GPL. Nothing prevents someone from taking GPL version 1.1 of the code and modifying it so it matches the functionality of private version 2.0. However, only the version path that went from GPL 1.1 to GPL 2.0 is covered under the GPL.

Use of PHP Under the GNU License

You are free to use PHP on any machine for any purpose without paying for software or making royalty payments to anyone . You can create any application with PHP and distribute PHP with it any way you want. You must provide the source code to PHP, or the ability to get it if you do distribute PHP.

The code you put on a Web page to be executed by PHP is not part of the GNU Public License. You can copyright it and protect it from copying by others by restricting its use through signed agreements. Under certain circumstances, that will be the only way to protect your work.

Any PHP code you write and put on a Web page is "in the clear" if someone has physical access to the machine it is installed on. Most of the code you put on a Web page is also visible to the person who views the Web page with a browser. If they use the View Source option available in all browsers, they will be able to see most of the code you write using PHP for that page.

A Web page that totally consists of PHP instructions might not show any of the underlying PHP code. This is done by creating your Web page using print instructions. This is an excellent way to hide the most critical PHP code.

only for RuBoard - do not distribute or recompile