Licensing and Copyright when Forking an extension (even one of Flarum's)
It's important to be aware of licensing when you fork (making a derivative work of) an extension. This applies even if you don't create a formal fork through Github or any similar service, or if you're forking one of Flarum's extensions. I'm going to use Flarum's English extension as an example here, as it's probably one of the most commonly forked extensions that Flarum has.
Disclaimer: Neither I, nor the personnel of Flarum, are lawyers, nor is this legal advice. Please take these guidelines for what they are, and understand that Flarum will not endorse nor prosecute any licensing violations. Extension devs must manage their own licensing and copyright.
Let's go to the flarum/flarum-ext-english repository on Github. You'll see in the main directory, there is a file called LICENSE. Many extension authors keep their license file in the main folder this way, so you shouldn't have to hunt far to find it.
As you can see upon opening, Flarum uses the MIT license. It's a very simple and permissive license, the only thing it requires is that any code you retain (you're modifying this, after all) is licensed the same and copyrighted to the original author. Your new work can have any license you want. There are other common licenses, BSD, GPL and so forth, that may have different requirements, so bear in mind to read the license and follow its instructions. If you need help interpreting, a simple web search will put you in easy reach of some simpler explanations of the legalese.
Now, let's say you've modified your code, and you're ready to publish it out. How do you license your code and respect the original? Well, you have a few choices.
- You can keep the same license, and add your copyright below the original. Here's an example of the copyrights if you do this:
Original work Copyright (c) 2015-2016 Toby Zerner
Modified work copyright (c) 2016 Your Name
You can use any name you want, your username, your real name, your company name. It just has to be an identifier of you.
- You can choose a different license (MIT is compatible with many other licenses, but double-check if you're working with another license for compatibility of the two). In that case, you would probably want to include your copyright and license on top, and the original copyright and license below in the same file.
- You can choose not to copyright/license your work, in which case it's recommended to modify the license file to read:
Original work Copyright (c) 2015-2016 Toby Zerner
This makes it clear that there are some modifications that are not copyrighted, for future forks.
Why is this important?
Flarum, and many of its extensions, operate with open source licenses, which are usually very permissive. However, this does mean that it's possible for someone to write an extension with a less-permissive license, and still use it and promote it on the main Flarum site. Extension developers will want to take care not to step on toes when creating forks of other extensions, as an extension with a less-permissive license may not allow forking, or have other requirements not included in the MIT license.
Copyright, according to the Berne Convention exists on a work from the moment it is "fixed" (created). No registration is required. This marks the work to its original author/contributors, and is important for establishing attribution and credit to the original work. Some people take copyright very seriously, so you should be mindful of this and take care to respect the existing licensing and copyright when forking an extension.
Hopefully this was useful to you.
