To Convert a Character Studio Biped to a BVH so you can import the Biped animation into Puppetshop,
you use the "Creature Export" button in the advanced section of the File Rollout.
This is the button with the purple bug on it. In the menu that opens up is a option called "Export a Biped To BVH"

It only supports Bipeds with a maximum of 4 spines bones and 1 neck bone.
Up to 5 Fingers are also supported.
All the biped bone names must be the default names biped gives them, as the 'Biped thief' with auto-rename them to
follow the default BVH names

Once you have generated the BVH you can create a (human) Puppet that matches the Biped in proportions and import the BVH onto
the puppet by using the human mocap importer.

** note you 'may' have to disable the "Map basePose 2 Puppet" checkbox in the advanced section of the file rollout.