I feel most people are fundamentally misunderstanding what forking means.
Generally, forking means making a copy and modifying it.
Github, however, seems to define "fork" as just making a copy.
So, in fact there is no "TOS violation". The license forbids making a copy and modifying it, while github requires that you allow making copies. There is no conflict between the two.
Even if it were, just having a license that contradicts the github TOS is not a TOS violation (unless that is separately mentioned somewhere).