I'm not seeing that, but maybe I'm misunderstanding something. [1] includes:
> we are also shared our change without reservation to every enthusiast (buyer).
Which to me says they're freely sharing the source with buyers. And I see in the GPL:
> For example, if you distribute copies of such a program, whether gratis or for a fee, you must pass on to the recipients the same freedoms that you received. You must make sure that they, too, receive or can get the source code. And you must show them these terms so they know their rights.
Which I understand as "you only have to share source code with buyers" (but they can do what they will with it).