[Tams80]

Which just paints an even bigger target on it.

When it was on its own website and hosted on its own servers, with mostly word of mouth (online) spreading it, Nintendo were probably not too happy, but accepting that it was legal.

But when Valve, who are sort of competing with Nintendo, host it and promote, that's another matter. Especially when many people do play games using it that they have not legally obtained.