Ajaxify Regions attempts to handle the problem of serving cached content for authenticated users. By default, page-level content is not cached for authenticated users because portions of the page layout may differ from one user to another. This module, while not currently addressing the needs of the content body, should allow full caching of the page using any full-page caching module (such as the authcache module) by replacing dynamic regions with ajax callbacks for user-specific - or otherwise uncacheable - content.
This module provides no useful functionality outside of a full-page caching context, but should simplify and expedite the caching of dynamic content (for authenticated users or user-specific blocks).
While this module was built with the best of intentions and proved useful in various instances, it was poorly (mis?) named. Eventually, the concept was commandeered by someone else and re-appropriated. It would have been nice if he had reached out (or would talk to us), but to his credit, his fork is better maintained (and upgraded) at this point. Feel free to take a look at Ajax Blocks for similar functionality.