I prefer to let VWD Cloth & Hair author reply on the mac subject, but I can speak about Carrara and Studio bridges. VWD Cloth & hair communicates natively with poser through poser Python interface. As you're a developer, I can talk shop. Technically, what the 2 other bridges do is to emulate this Python layer and translate it in a way understandable by the other product. For Carrara, it's done by adding a Python interface to Carrara. For studio, it's done by translating on the fly the Pyhon script sent by VWD into QTScript that can run in Studio (given a QTScript object layer reproducing Poser object layer).