In order for the Finder to display Open / Drop states correctly, you need to make sure you set IconBuilder to save as a folder with a custom icon applied to it.
Once this is done and you save the icon to the desktop, try dragging a file or folder onto it to see the Open / Drop state in action.
If you still do not see the folder animate, try re-saving the icon using a different name. The Macintosh OS X Finder has a tendency to cache old versions of an icon and may not display it properly unless the icon is saved as new.
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