Notice: No Longer Maintained
As of OS X 10.11 (El Capitan) and Safari 9, the DeliciousSafari plug-in will no longer load due to a privilege violation.
DeliciousSafari was developed when input manager plug-ins were the only way to add extensions to Safari. Since then, Safari has release an official extension developer SDK. Since it was first written, DeliciousSafari had to adapt to security changes made by Apple, moving from an input manager plug-in to an Apple script extension.
Also, about a year ago, delicious.com broke backwards compatibility by requiring OAuth, vs Basic HTTP Authentication over HTTPS that DeliciousSafari relied on.
Both the Apple security changes and Delicious.com changes make sense for improving end user security, but in the process have obsoleted the approach taken by DeliciousSafari. Thus, this project will no longer be maintained. However, the code will still be available on github.