copyright

I believe that is true but you can create a fair usage licence – where you can request that the script, if used, must include credits for the original author of the script – you find it better to consult the php forums rather than WordPress as this is a technically legal issue and PHP would be best poised to provide the correct answer

DISCLAIMER: I am a lawyer, but I am NOT your lawyer. What follows is speculation, and is NOT legal advice. If you plan on writing and distributing either source or object code and are concerned about these issues, please consult your own lawyer.

First, under what license is PHP released? Different versions of PHP have been released under different licenses. Early versions of PHP 3 were released under the GPL. For whatever reason, the developers decided to release later versions of PHP 3 under a license based on the QPL. The QPL, like the LGPL, is a license designed to cover code libraries. A code library, for those of you who are unfamiliar with the term, is a program, like PHP, which contains functions that other programs can rely on.

The PHP developers changed their minds again, however, and released PHP 4 under the the PHP License version 3.0, which they apparently wrote themselves. The new license is very sparse, and is not explicit about what a software author needs to do to comply with the license when releasing a script based on the code. The new PHP license contain three basic restrictions.

First, redistribution of either source or binary code must contain the copyright notice and conditions of the PHP License, version 3.0. However, the license does not define what code is covered by such a redistribution. Because it’s undefined, I would argue that this restriction in the license covers redistribution of PHP itself, not of any software which uses PHP. This is supported by the fact that this restriction does not refer to “derived” works, as do later restrictions.

Second, a software author may not use the name “PHP” name, endorse, or promote any products “derived from this software.” In other words, a software author can’t call his piece of software, derived from PHP, “PHP Foo.” However, the license does not instruct a software author on how to determine if their product is “derived from” PHP.

Third, the license requires that “[r]edistributions of any form whatsoever must retain the following acknowledgment: This product includes PHP, freely available from <http://www.php.net/&gt;.”

These restrictions, unlike those in the GPL, do not appear to impose any requirement that a script which uses PHP functions must be licensed under the same license. In other words, a software author who writes such a script should be able to write and release a script which is licensed under any terms he or she chooses, including GPL, CC, etc.

What if PHP were licensed under the GPL? Would a software author have to release his or her software under the GPL as well? I think the answer to that is probably not. There are two kinds of code libraries. The first allows a software author to actually incorporate pieces of the code library into his product and distribute the completed product in executable form. The executable would actually contain chunks of the code library, and would be a stand-alond product. In that case, the product is almost certainly a derivative work of the code library, and must be released under the GPL, if that’s the license under which the code library is released. However, a script which uses PHP commands does not actually incorporate pieces of the PHP code library. Instead, a PHP script relies on an external installation of PHP, installed on the same server. Because the code library is external to and not included in or distributed with the script, the script is probably not a derivative work and can be released under terms chosen by the author. This guy, also a lawyer, agrees.

Remember, legal advice must be provided in the course of an attorney-client relationship specifically with reference to all the facts of a particular situation and the law of your jurisdiction. Even though I am an attorney, you must not rely on this post as a substitute for obtaining specific legal advice from a licensed attorney.

Thanks, Jinsan, I hope this is helpful. The most important lesson, I think, is to make sure you read and understand the license to the software you are using to develop your own software. For most WordPress users, this is important when using and modifying a theme released under a license like the GPL. Understanding what your obligations are when you modify, use, and redistribute a theme is important.

That’s one of the things I like about the CC licenses. While they have all of the important legal text, they also provide succinct clear english summaries. For example, see the Creative Commons version of the GPL.