An appropriate analogy in this case would be someone putting up a sign that explicitly says that nobody has to thank them, then getting mad that nobody thanked them.
The problem with this is that it disincentivizes the sharing mentality. Nobody wants to be the guy who gets taken advantage of, yet everyone benefits from free sharing of knowledge. And then once in a while you have dudes who swoop in and make everyone look stupid and make them re-think whether they should ever share their findings with others again.
Obvious could make this right if they wanted to. Yet they are standing their ground on Twitter, it seems.
This loses the important nuance that them swooping in and slapping a price tag on their own use of the implementation doesn't deprive anyone of access to the original on the same terms they were able to access it.
No one has lost anything in this scenario.
>The problem with this is that it disincentivizes the sharing mentality.
Personally, I feel arguing over how people make use of freely shared knowledge does more harm a culture of sharing than usage of said knowledge, even when that usage pushes right up to the bounds of what is allowed under whichever license.