Eradicate my ignorance!: Why must my plugin be “compatible with the GPL”?

It’s just saying if your theme / plugin is tied to WordPress in any way it must be that way because WP is GPL.
If you can do it without any WP code or calls, I suppose you could do another type license.

Really? So, for example, if I create a theme that contains ‘the_content’ then it has to be GPL compatible?

No – it’s more complex than that.
Others will answer more fully yet.

Plugins and themes don’t HAVE to be compatible with the GPL.

However, to the extent that you used WP’s copyrighted code in yours, yours will be bound by the GPL.

Where to draw the line is the tricky issue (ie. how much code do you have to use that’s from WP before it comes under the bounds of copyright protection).

I wouldn’t worry about it too much. Nobody’s going to sue someone for a GPL claim over a random plugin or theme, it’s unfair to do so.

I really don’t think it legally has to be GPL compatible, it’s 100% your own code, just calling functions it WP, there’s no legal reason for it to have to be GPL, never mind the random codex contributor.

I’m with Firas. It’s a gray issue, not well defined by any GPL literature. Most GPL lit doesn’t even deal well with scripting languages, let alone the concept of plugins within a scripted environment.

This thing gets asked time and again, and there is no answer. Maybe the next GPL version will deal with the topic better.

However, at what point is a ‘plugin’ just a way to connect up two systems? At what point are the two systems disctinct entities that don’t ‘rely’ on each other except for some basic interaction? (Examples: something like retrieving the core WP site URL, which would be needed for building URLs to your code or other path work; or installing a hook so that your code gets called automatically without template modifications, but your core code doesn’t actually otherwise ‘talk’ to wordpress in the slightest…)

-d

Well, I’m glad I’m not the only one confused. Perhaps the codex should be altered to reflect this confusion. My ignorance has been eradicated. However, I have now been discombobulated. Thanks for the responses so far!

Perhaps the codex should be altered to reflect this confusion

You are right, and feel yourself invited to add a more documented explanation to the Codex ?? As you know, it’s a community effort and its format/tool makes possible editing.

Sentences are already forming in my head…

Finally, a thread with an intelligent discussion about WordPress/plugins/themes and the GPL.

Here is my updating of the Codex page for writing a plugin. Any comments?

Before:

You do not need to license your plugin under the terms of the GPL (https://www.gnu.org/copyleft/gpl.html); but any license you choose to use must be compatible with the GPL (https://www.fsf.org/licensing/licenses/index_html#GPLCompatibleLicenses).

These two sections can then be followed by the function definitions and the actual plugin code.

After my edit:

The licensure of your Plugin should be weighed carefully. This issue is somewhat of a grey area and subject to debate within the WordPress community. The general consensus is that plugins should be licensed under the GPL (https://www.gnu.org/copyleft/gpl.html), or a license compatible with the GPL (https://www.fsf.org/licensing/licenses/index_html#GPLCompatibleLicenses), although this is not legally required to write and publish a plugin.

Regardless, these two sections can then be followed by the function definitions and the actual plugin code.

I may be mixing apples and pcs, but there are commercial theams and modules for the open source ‘Joomla’ CMS. I can’t afford to get any of them, but it helps me knowing that when I can they will be out there. I love what I can do with WordPress, but wouldn’t that be extended if there could be commercial theams and plugins?

Thanks, Scott Newkirk
university.if4.us

Yes. There can be commercial themes. Although the above blurb doesn’t explicitly say so, at least it no longer says things have to be GPL’d.

You could always do ‘commercial’ releases of GPL stuff. You just needed to make sources available for free as well.

IF a court at some point actually determined the ‘line’ past which something must be GPL’d because it is used alongside a GPL’d script, and ‘the line’ was determined to apply to the average theme or plugin (that references more than x core function calls or something), it is possible that anyone doing Joomla or other themes and modules would need to re-badge as GPL and provide the sources under the GPL.

Also, if you ‘buy’ something that is commercial AND GPL, note that the GPL allows redistribution… Fun.

Proper leveraging of GPL stuff makes bigger companies/entities money, and in many cases makes smaller groups and individuals, though in just as many cases individuals are making absolutely nothing… ??

-d

I think if you are making a plugin or themse for WordPress AND you decide to release it to the world, then you need to make it available for free, even a less gpl would be ok. The programmers who made wordpress made it for free and without wordpress, the themes and plugins are just some lines of code that do nothing.

If instead of releasing the themes or plugins, you just use it on your own site, then that is ok, keep it to yourself. Don’t advertize that you will sell it. And if someone comes along as says, hey that is cool, can I buy it? Then you should be able to sell it with a gpl, meaning the guy you sell it to could publicly release it to the world.

I don’t know nuances of the GPL, the comments above are just based on my own sense of right and wrong.