I finally upgraded the Mac Pro to 10.6.6.
They put an App Store icon in my dock, which I immediately removed.
I loaded the App Store and all of the free applications are rubbish. However - and I find this interesting, it has detected several apps as Installed - ones that I downloaded directly from the developers' and ones that came with the Mac, such as TextWrangler and iPhoto.
I'll download Xcode eventually and start researching on how to add a "Build for App Store" menu item to SilverCreator. The plan is to do it in such a way that you do not need to use Xcode at all, you will only need to have it installed. SilverCreator will then build your game, strip out the PPC code, execute the necessary commands to package it, etc.