The author is not taking the metaphor far enough! He left out one of my favorite pieces of Mac OS.
The folder should not contain application launchers. It should contain the actual applications themselves. An application is just a file. To "install" an application, copy the file to a location on your hard drive. To "uninstall" an application, delete the file.
Under the hood, applications can be a collection of files, whatever, but the GUI should treat each application as one file.