I'd call it offensive purely for putting his knee through the other guy's head. No need for that.
Its worth noting that under FIBA rules he is outside the no-charge area. By NBA/NCAA rules he is inside the no-charge area.
After doing some hunting around it looks like this should still be an offensive foul because the guy taking the charge is the primary defender, so the no-charge area does not apply.
http://aol.sportingnews.com/ncaa-basketball/story/2011-11-08/new-no-charge-arc-to-clean-up-play-in-the-paint
Forte: "Understand, this applies only to the secondary defender. The primary defender is defined as facing the player with the ball, and there's no required distance — I can be 30 feet from you, but if there’s no one in front of us, I am the primary defender, as long as there is a clear path. The secondary defender is defined as picking up the offensive player."