I haven't seen anyone else post this link, so here goes: Sandy Lodge created a free utility called Obaction Mover for Windows that quickly enables Poser v3 and up users to import an obj model as a fully jointed and poseable Poser figure.
and this has been ported to the Mac, too...
The util is not exactly well-documented, so here goes my version: You use a Poser 4 figure as the seed model, specify your obj file as the difference model, and then Objaction Mover creates a hybrid file (the mesh becomes original, thus eliminating copyright issues). Take the new file and decode it, producing *.cr2, and a Poser resource file. Put them into the existing folders in Poser, access the new model through the Figures menu, Poser will prompt you for the obj resource file, tell it where it is, and then save out your new creation in Poser format.
I had modeled Darth Vader a while ago, and successfully applied a walk to the new figure!
It was very entertaining to see Darth stroll...