You can access Poser's weights through Python, see the methods JointVertexWeights (Get a list of vertex weights for the specified joint axis on this actor) and TwistVertexWeights (Get a list of vertex weights for the specified twist axis on this actor). Be aware though that Poser uses separate weights for every rotation axis, where most other bone systems use only one weight for all axes. That's why any translation of a Poser rig to many other bone systems will only be a compromise and can't reproduce the behavior of a Poser rig, weight map or not. Ask kuroyume why he wrote his own bone system for InterPoser Pro instead of using Cinema 4D bones.