DreamWeaver MX has no autosave function. This tool implements it by 'clicking' on the Save, or Save All menu items for you (at a regular interval). It is a stand-alone program, not a DreamWeaver MX plugin.
The HomeSite Extensibility Project (HEP) is aimed at developing a series of useful extensions for Allaire's Homesite 4.5+ using the scriptable object model provided by Allaire, with a heavy emphasis on XML/XSL tool development.