Distributive Laws and the Koszulness

We study algebras with a distributive law and the Koszulness of associated operads. As a corollary of our theory we prove that the homology operad of the little cubes operad is Koszul, the result which was originally proven by E. Getzler and J.D.S. Jones in their preprint "Operads, homotopy algebra, and iterated integrals for double loop spaces" using the combinatorics of the stratification of the Fulton-MacPherson compactification of the configuration space. Since the above mentioned result whose purely algebraic proof we give plays and important role in closed string field theory and especially the methods used in the original proof of Getzler and Jones are very relevant for this part of mathematical physics, we decided to put our paper here, though some 80% of its material belongs rather to universal and homological algebra.