So, if I get the CD version of Pro Pack at $139, I get both Windows and Mac versions. If I get the download version of Pro Pack, I have to spend $139 for each? Something strange there. Having the Windows version already, how do I get the Mac version without paying another $139? This is solely for product testing purposes as I have other uses for my new Mac. Everything 3D is done on my Windows system.

Try asking CuriousLabs. Perhaps they could do something like a replacement CD that would probably include both versions

IIRC the CD having both versions on was a manufacturing convenience - I THINK that the EULA or license or whatever was for either or, not both (to the extent that when I bought P4 I had to specify Windows or Mac IIRC, despite it being physically the same dual-format CD). This does appear to have been flaunted and ignored an awful lot tho.

Well, to avoid wasting time, I just ordered the PP version for Mac and was done with it. For testing purposes, I'm not really inclined to purchase all of the software twice. This is not a matter of using on both platforms as much as having a testing platform for Mac products. Although there are other options (such as using someone who has a Mac as a beta-tester), having a Mac test platform at my immediate disposal is much more expedient and any problems will be less ambiguous to understand and easier to fix.