  Modified gravity (MOG) is a covariant, relativistic, alternative
gravitational theory whose field equations are derived from an action that
supplements the spacetime metric tensor with vector and scalar fields. Both
gravitational (spin 2) and electromagnetic waves travel on null geodesics of
the theory's one metric. Despite a recent claim to the contrary, MOG satisfies
the weak equivalence principle and is consistent with observations of the
neutron star merger and gamma ray burster event GW170817/GRB170817A.
