  We discuss the reduction of the open membrane metric and determine the
(previously unknown) conformal factor. We also construct SL(2,R) invariant open
string metrics and complex open string coupling constants by reducing the open
membrane metric on a 2-torus. In doing so we also clarify some issues on
manifest SL(2,R) symmetry of the D3-brane. We remark on the consequences of our
results for the recently conjectured existence of decoupled (p,q)
non-commutative open string theories in type IIB string theory.
