It's possible that I'm misunderstanding the question, but I don't "think" zsculpty has anything to do with smoothing, as it's merely for exporting a sculptmap from zbrush to use in second life (but yes, for PC's only).
If you are using zbrush on a mac, then you already have some great smoothing tools in the program: on the deformation tab (between Noise and Inflate) is the Smooth slider; there's also a Smoothing brush in the brush palette.
If you are wondering about exporting your sculpties from zbrush on a mac, then the only way I know of is:
1. make a sculpty sphere (or other sculpty shape) in Blender or Wings,
2. export that as an obj.,
3. import that .obj into zbrush,
4. do your sculpting on that shape,
5. export the finished shape as an .obj from zbrush,
6. import the finished shape back into the same program you created the original sphere and use that program's export to second life scripts.
Hope that helps and/or makes sense
