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Plugins and GPL WordPress


I've done countless searches throughout the web on the generalities of GPL and such. I have a decent idea of how it works, but there are still foggy details that I'd like someone to clear up for me.

Let's use the Shortcode Ninja plugin by woothemes as an example. They used the legwork of a guy that created Shortcode Generator, and made a custom plugin for their websites that distributed under the GPLv2.

Is that plugin completely open to be customized and redistributed under GPLv2?

Is all of the code included in the plugin, the JS files, etc encapsulated in the GPLv2 ?

If I were to hack and customize the plugin, and use it in a commercial theme, is there a strict way to credit the original work? Is it required to credit the original work? If so do you credit the original they credited AND the derivative you edited?

Hopefully you guys can shine some light on these details.

Thanks a bunch.

Answers (2)


Denzel Chia answers:


As long as it is GPL code, you will need to license it under GPL, irregardless of whether free or commercial. And the whole plugin, the program as a whole, must be GPL too.

As for crediting original work, there is no need to.
But it is good to put a comment on the program code itself to attribute credit to original work.

For your information, I had done many commercial plugins for my clients, as well as a few free plugins under my name.


Denzel Chia comments:


The following is an excerpt from GPL FAQ.

<strong>If I use a piece of software that has been obtained under the GNU GPL, am I allowed to modify the original code into a new program, then distribute and sell that new program commercially?</strong>

You are allowed to sell copies of the modified program commercially, but only under the terms of the GNU GPL. Thus, for instance, you must make the source code available to the users of the program as described in the GPL, and they must be allowed to redistribute and modify it as described in the GPL.

These requirements are the condition for including the GPL-covered code you received in a program of your own.


Joe Jenkins answers:

You must release any WordPress theme or plugin as GPL, as it uses core code from WordPress, which itself is GPL.

You do not have to give credit for previous versions.

The thing to remember, is that if you do this, don't get upset if somebopdy comes along and then takes your plugin and makes changes which they then release as GPL without giving you credit.