Oomph! I'm afraid you would very likely have similar problems with Wings3D, as well. If Poser exports vertices that are not used in polygons, I'm almost certain Wings will ignore them and not include them in the export. Also, Wings has no concept of groups at all. If there are groups in the obj file but no objects, it treats the groups as objects. If there are objects, it ignores the groups. The usual trick is to convert groups to materials before importing into Wings and back to groups after exporting. Or one can use UVMapper to save and remove the original grouping information and add it back before importing the morphed mesh into Poser.

Yes, Wings is free and open source (but written in Erlang, which I am not familiar with).

-- I'm not mad at you, just Westphalian.