I installed 'Safari Cookies 1.9.8' (downloaded from your download page).
The 'Safari Cookies.bundle' is present in the SIMBL Plugins folder and the 'Safari Cookies' UNIX executable is present in the bundle.
But where is the user interface? How is it used?
There is no Safari Cookies app in the Applications folder. There is no Safari Cookies Preference Pane in System Preferences. I can find no mention of Safari Cookies in Safari Preferences or in any of Safari's menus.
OS X 10.6.8, Safari 5.1.9, 12 Gig of ram, 41 Safari windows open with 6 tabs across two monitors
A ReadMe file might be helpful, or even some screenshots on the download page.