If M and/or N are direct sum modules (isDirectSum M == true) then H is the direct sum of the Homs between the components. This SHOULD be built into Hom(M,N), but isn't as of M2, v. 1.7
The object HomWithComponents is a method function.
The source of this document is in /build/reproducible-path/macaulay2-1.25.06+ds/M2/Macaulay2/packages/CompleteIntersectionResolutions.m2:2645:0.