While I've run across lots of information on how to use Poser models in Bryce, I can't find any instructions on reversing the procedure. Pardon me if this is a stupid question, but are there any methods for converting Bryce obp's and material textures into Poser 5 or 6?

The latest version (6.0) is the first one that allows you to convert booleans to mesh and thus export them (fiddly but possible).
Previous versions have allowed export of previously imported meshes (also rocks and terains/lattices).

There isstill no (easy or otherwise) way to get materials out of Bryce, so you'll have to redo the materials in Poser.

You can't convert an obp file, but you can take your boolean model and turn it into an obj file (there is now a "C" at the bottom of the object menu that I would assume stands for "Convert to Mesh").

Once you have converted the object to a mesh, you can export it, and then import it into Poser.

I looks like Bryce also creates UV maps for the saved obj, although I'm going to have to look into that a little further.  I was playing with creating some boolean models in Bryce and I suddenly found all sorts of UV maps had been created ... but, when and how, I have no idea.

If you looke at the product description for this:

http://www.renderosity.com/mod/bcs/index.php?ViewProduct=51980

the merchant gives a nice description (I haven't tried it yet) of how to get both
the model and the texture out of Bryce for use in other programs.

Hope that helps :)

Thanks to everyone for the help!