PHP License
Reason the license was written: PHP Group wrote this license. It is used for programs which are written using PHP (stands for "PHP: Hypertext Preprocessor"). The PHP License’s goal is to define the way of redistribution and use of PHP. It is mentioning how to redistribute it, how to use the name “PHP”, how to comply with each version, its liability, etc.
Compatibility with GPL:
It complies with some essential principles in that it is mentioning derivative works must be distributed under that same license, it can not modify the list of the license implicitly, and copyright holder may choose to add any later version to the distribution terms in order to allow distribution under future versions of the license.
However, it is missing some important points as well. It does not mention anywhere that covered works that are distributed must be accompanied by the source code. Rather, it is saying redistribution of source code, and binary form, respectively. This can be translated that binary code alone can be distributed. This is completely not compatible with the GPL. Also it does not say that any additional clause can not be added to this license. This can seriously harm the GPL. Another problem is that it does not mention royalty-free license for any patents in the software, which can be put into bad use of it.
Derivative Works:
Derivative Works must be distributed under the same license. It says that redistribution and use in source and binary forms -with or without modification- must retain copyright notice, the list of conditions and disclaimer.
Covered Works:
Covered works that are distributed must be accompanied by the source code, or offers methods for access to it. It does not specify this anywhere. It just says that binary form must be redistributed with copyright notice, list of conditions, and disclaimer in the documentation and/or other materials provided with the distribution.
Charging money for the programs under the license:
There is no specification for including source code, and restrictions on charging money as well. If this license is to follow GPL more faithfully, it should include clause about source code which I mentioned above, and also no restrictions on charging money.
Including a copy of the license:
It says in clause 1, 2 that redistribution must retain copyright notice, list of conditions, and the disclaimer in the documentation and/or other materials provided with the distribution. This is saying that it can not be modified at all implicitly.
Adding to the license:
It only says that redistributions must retain this license. I can assume that they do not permit any modification implicitly. However, it does not mention anything about adding additional requirements or restrictions to those stated in the license.
Distribution under the license:
It does not specify about patents explicitly. Even further, it does not mention anything about royalty. This can mislead people to take advantage of patents in the software in order to get royalty from it.
Later Versions:
It says that it may publish revised and/or new versions of the license from time to time in clause 5. Furthermore, once covered code has been published under a particular version of the license, they may always continue to use it under the terms of that specific version.
Other Relevant Aspects:
You may redistribute binary form alone. It does not specify that binary should be redistributed with its source code.
You may not use “PHP” in your product’s name directly. It specifies the use of the name “PHP”. “PHP” can not be used in a way like “PHP Foo” or “PHPFoo”. Rather, it may be used like “Foo for PHP”.
You may add additional requirements or restrictions to those stated in the license. It does not specify prevention clause anywhere, so it can be misused this way.
You may earn a royalty for patents in the software. It does not mention this important thing, so it can be put in bad use like this.
Reviewed by:
Kyo Seok Song,
Carnegie Mellon University