What does it do?
The full name is "Harven's Addon Settings to LibAddonMenu-2.0 Adapter" and it says it all
This adapter removes the second main menu entry "Addon Settings" and merges the settings pages into one main window.
Both libraries, Harven's Addon Settings (most recent version can be found in Harven's addons) and LibAddonMenu-2.0, are a framework to simplify creating addon settings. Although it is technically correct, many people think it is a "bug" having two main menu entries called "Addon Settings". Especially, if they just use one addon using "Harven's Addon Settings" library.
This version of "Harven's Addon Settings to LibAddonMenu-2.0 Adapter" is re-written from scratch.
It offers full API compatibility to addons using LibHarvensAddonSettings and integrates them to LibAddonMenu-2.0.
You should not experience any change in behavior or missing features and at the same time have one "Addon Settings" main menu entry only.