The key wording is undisturbed. In other words they did testing leaving hep c infected blood undisturbed and determined it was still infectious after three weeks.
However, what in the real world remains undisturbed and bear in mind hep c infected blood must enter the blood stream of an uninfected person through an open, fresh, wet, weeping injury.
Hep c is not in general very contagious if it were many more than the less than4% of the US population would be infected.
Curious why your friend is not seeking treatment. There are new treatments approved since 2014 that are much more effective than the old interferon treatments boasting cure rates of more than 98% for most patients. The treatments are much better tolerated then the old as well.
His treatment could be as simple as 1 pill a day for possibly as few as 8 weeks and he could be cured.
Have you noticed any TV commercials for Harvoni or Epclusa?
Also most of us who were infected with hep c tried to be very careful when we would have an injury to avoid the risk of infecting those closest to us.
But no you are not at risk unless you decide to become blood brothers or share IV drug needles with him