URL says there is a version 2.0 but creates error. Is 1.6 the latest version?
I've checked the official website and it appears that version 1.6.4 is the latest one available for downloading from the official website. Access the website listed below and then download the DMG file.
Download page: http://www.everydaysoftware.net/showdesktop/
If you have trouble downloading the file, use this direct link: http://www.everydaysoftware.net/download/showdesktop.dmg