Modules and Morita theorem for operads

Associative rings A, B are called Morita equivalent when the categories of left modules over them are equivalent. We call two classical linear operads P, Q Morita equivalent if the categories of algebras over them are equivalent. We transport a part of Morita theory to the operadic context by studying modules over operads. As an application of this philosophy, we consider an operadic version of the sheaf of linear differential operators ona a (super) manifold M and give a comparison theorem between algebras over this sheaf on M and M_{red}. The paper is dedicated to A.N.Tyurin on the occasion of his 60th birthday.