It's Not Copyleft

Sat, 1 Oct 2016

Someone recently pointed me to Jonathan Riddell's blog post "In Defence for Permissive Licences; KDE licence policy update."

In there he seems to be claiming that any free software license that requires preservation of the license notice (and almost all do) means that anyone getting a copy gets those original permissions. Essentially that all such licenses are some form of copyleft. This is nonsense, as I'll explain.

But first I wanted to mention that he seems to contradict himself.

In paragraph #3, while he's making the claim, he talks of misconceptions: "One is that it allows you to claim additional restrictions to the code and require anyone you pass it onto to get a different licence from you. This is nonsense..."

But then when talking of MIT he says "you can even sublicence it, make a additional licence with more restrictions..."

So which is it? Can you add more restrictions or not?

Anyway: You can, as I'll explain.

His whole point is that the license requires the notice to remain there. So what? Yes, someone may voluntarily pass on the source code and the freedoms to copy, modify, etc. but they're not required to. They're only required to include that particular blob of text, not to actually give you those permissions. There is a subtle difference.

Because, just like the license says, it can be sublicensed. Let's imagine a program under a proprietary software license that also just happens to incorporate some code under MIT. Let's also imagine that said proprietary program just happens to come with source code and so you can see the source and that blob of text from the MIT license.