[detaro]

They add value (for people who like video tutorials) and offer an alternative, so why shouldn't they be able to charge for it? They don't just take free content and try to resell it slightly repackaged (at least as far as I know) and they compete fairly with free resources, so I think that's ok.

RE license: As long as they don't copy directly from the documentation or the examples, the license shouldn't really matter. And even then, at least some examples from the docs might be to trivial to protect (you won't succeed claiming to own the code snippet "list = [1,2,3]" or similar). I don't think you can have a successful language aimed at the public and at the same time successfully forbid people from creating third-party documentation for it.