If you are familiar with bitcoin scripts then you can think of OP_SUCCESS as something very similar to OP_NOP. We already have a couple of them in bitcoin, for example OP_NOP2 which made activating OP_CheckLocktimeVerify possible through a soft-fork. The only difference is that OP_NOPs don't do anything (interpreter simply moves to next OP) but OP_SUCCESS stops there and returns TRUE no matter what comes next.