Poser used to be sold as as a hybrid.  You received both the Windows and Mac versions.  My P4/PPP, and P5 were all purchased as physical disks.  My P6 back up disk I purchased from Digital River was also a hybrid listing Mac and Win versions on it.  I clicked on the buy link and when you go to the purchase page, you don't have to specify whether you want Win or Mac so SMS may be offering both versions in download price.