While I think this is extremely shady and will avoid ever using a tool like this in the future, does it actually break google's TOS? It seems like a valid defense could be made.
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As others have pointed out and the author acknowledges, he is technically injecting links when his users embed their scoreboard on their website through an auto-included link-back to his site.
Now, I don't frown upon this. It is not deceptive and its placement is more than relevant.
The same cannot be said for the scheme the author uncovered. But whether it is violating Google's TOS is another question. I'm not sure of the answer.