[ElevenLathe]

Can you name one? A sibling comment says the MIT license is one, but that requires derivative works to include the license, so it seems also to be copyleft under this definition. What is the point of releasing software with a license that says you can strip the license off of it and do whatever you want? This is effectively the same as releasing it to the public domain.

[leereeves]

The MIT license requires attribution (in the form of the copyright notice and the license file) for the MIT licensed code.

But it doesn't require that other code in the project be released under the MIT license (or even released at all), which is what copyleft would do.

It's pretty close to releasing it to the public domain, and the point of that is that it's actually really hard to release something to the public domain worldwide. Just saying something like "I release this code to the public domain" doesn't have the same effect in every country.

[ElevenLathe]

Interesting, I've never encountered this extremely narrow definition of copyleft. Thanks for explaining.

[ben_w]

MIT isn’t copyleft.

If you want to include an MIT licensed work in your project, your obligation is to say “I am using $foo, here is a copy of the MIT licence: $text”, and that’s it.

If you want to include a GPL licensed work in your project, your project is now also GPL licensed, and you are obliged to make the source available.

(I’m not a lawyer etc.)