Linux, AVFoundation and Lion.
While Linux plugin can be used alone, the other two plugins have references to Cocoa plugin. So in order to use them and have projects compile you need to install the required plugins (Cocoa, CocoaBase, Leopard, MacOSXCG and MacOSXCF).
With Lion plugin alone you can of course just use the new Mac App Store receipt classes. For AVFoundation plugin you can only use a few limited features without other plugins, like opening a video and reading meta data.