I’ve bought, downloaded and supposedly installed two stacks (one called Photo by Nick Cates and one called Gallery by Instacks). I’ve double clicked on the stack icon and got confirmation and I’ve dropped the stack icon onto the RW icons on the start bar (both RW7 and RW8) and get a little success message. But they do not appear in the library.
I also downloaded a Nick Cates theme called Iris. It didn’t install using the unzip/double click method, but it did when I dropped it onto the application icon.