  The physical states of D=5 holomorphic Chern-Simons theory correspond to
on-shell D=10 open superstring states in the cohomology of $q_+$, where $q_+$
is one of the 16 spacetime supersymmetry generators. Scattering amplitudes of
these states can be computed either using the usual Ramond-Neveu-Schwarz (RNS)
superstring prescription with N=1 worldsheet supersymmetry, or using a
topological $\hat c$=5 string theory with twisted N=2 worldsheet supersymmetry.
  It will be argued that the relation between D=5 holomophic Chern-Simons and
the RNS superstring is identical to the relation between the the pure spinor
superstring and the recently constructed B-RNS-GSS superstring which has both
N=1 worldsheet supersymmetry and D=10 spacetime supersymmetry. Physical states
of the pure spinor superstring correspond to on-shell B-RNS-GSS states which
are in the cohomology of $\lambda^\alpha q_\alpha$, where $\lambda^\alpha$ is a
D=10 pure spinor. And scattering amplitudes of these states can be computed
either using the full B-RNS-GSS superstring prescription with N=1 worldsheet
supersymmetry, or using the pure spinor superstring amplitude prescription with
twisted N=2 worldsheet supersymmetry. This should be useful for proving
equivalence of the RNS and pure spinor amplitude prescriptions and for
clarifying the relation of their multiloop subtleties.
