Which "Win8 Start Button" do you have in mind? The one that we have listed doesn't look anything like Classic Shell:
Then you haven't been customizing Classic Shell to see how much it can be customized. Anyways, here's the EULA for Viva and here's the one for Win8 Start Button.
The Win8 StartButton that you linked to, doesn't appear to be the same product as the Win8StartButton that's on the list. Different website, different people (Torch Media vs. Quadsoft), different look, even a different language (!).
There's just a slight difference in the spacing within the name. Given the outrages of Windows 8, I guess it was inevitable that we'd end up with a naming conflict like this sooner or later. There's only so many ways to refer to the same thing.
I won't be listing Win8 StartButton, as it seems to be a straight, unmodified borrowing of Classic Shell, nothing new. What's different is that they package a browser and media player along with Classic Shell, but we're not interested in those applications here.
Regarding the Viva Start Menu, the EULA says that
...which leaves open the possibility that they have "built upon" Classic Shell rather than adopting it intact like the Win8 StartButton folks apparently did. The question would then be, how much did they change it, and are the changes enough for us to be able to treat it as a different product?