By the book, it was a moving screen, but IMHO, moving screens are the most inconsistently called fouls in the NBA. I did not watch this game, but am willing to bet there were other moving screens just as bad that went uncalled.
Seriously, Anderson Verajao would foul out of every game if all refs called this every time it happened.
I should also say that the one Big Baby fouled out on the other night was NOT a foul.