There has been no statement by the Opensc.ws site admins, the hackers are not verified at this moment, but the defacement page lists three names, GOA, 3lite, M-$p33d. The message left on the site is below, and at the time of this posting OpenSc.ws is still defaced.
The deface message that has been left:
Give b*tches some fame, b*tches love fame: GOA, 3lite, M-$p33d isn’t it almost orgasmic? x3