I found the vendor of the "spirits" product. It might be from PoserPros. The vendor was Cyllan. Among other things, you could make the figure more transparent on the bottom.  It was specific for the unimesh figures, though.

It's not a script, and it does work in Poser 12. Though the shaders end up glossier than they did in older versions of Poser, especially if you render in Superfly. Cyllan has some products at PoserAddicts, but not this one. He had some stuff at Content Paradise for awhile, but doesn't seem to be active in Poserdom any more.