I'm working on a project and an existing plugin (from the WordPress repository) has most of the features I need, but there are changes that I need to make to the plugin in order for it to meet my requirements. It's my understanding that if a plugin is released under the GNU Public License, that it can be freely modified. But what if the plugin has no mention of a license? I was initially under the impression that everything released in the WordPress repository is under that license, but I'm struggling to find an official source with that statement for plugins.


You should ask your lawyer, never ask legal advice from random people on the net.

Regardless of the legal question, it is rarely a smart idea to fork a plugin unless you understand that from that point forward it is your plugin. You can smartly use GIT to manage synchronizing when the original code updates, but the more changes you make to it, the harder it will become.

This might not be a biggy for a 100 LOC plugin, but will be much harder to maintain if the plugin has 10k LOC. Foe example yoast right now has a new version at least every week, are you really going to merge the code bases every week? that is going to add an overhead to you developent process.

Forking of plugin or theme should be the last thing on your mind regardless if its legal or not.

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You're correct, all plugins from wordpress.org have to be GPLv2 or later

Plugins must be compatible with the GNU General Public License v2 or later. If a license is not specified, code will be considered “GPLv2 or later.”

If you don't see the licence outright, you can explore the plugins source code on the repo with


Where "{plugin_slug}" is the slug of your plugin, like my-plugin. You'll be looking for a file like LICENCE.txt or check out readme.txt there should be a License: x in the first few lines. Also the main plugin .php file (differs for each plugin, but usually shares the same name as the plugin slug) may mention the licence.

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  • License actually have nothing to do with the OP's question – Mark Kaplun Aug 16 '18 at 16:34
  • Whatchu talking about Mark? he mentions "licence" 3 times and even has it as a tag. – David Sword Aug 16 '18 at 16:38
  • that is because technical people understand zero about law and therefor do not even know how to properly phrase what they want to ask. – Mark Kaplun Aug 16 '18 at 16:39
  • to be explicit the answer is probably "yes" regardless of the license for 99% for the cases – Mark Kaplun Aug 16 '18 at 16:41

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