The aim of this sequel to [10] is to set up the cornerstones of Koszul duality and Koszulity in the context of a large class of operadic categories. In particular, we will prove that operads, in the generalized sense of [7], governing important operad-and/or PROP-like structures such as the classical operads, their variants such as cyclic, modular or wheeled operads, and also diverse versions of PROPs such as properads, dioperads, 1 2 PROPs, and still more exotic objects such as permutads and pre-permutads are binary quadratic, and describe their Koszul duals. We then prove, using the results of [11], that operads describing the most common structures are Koszul.