From the Gumroad:
This add on is to transfer mesh data from a target to a specified source based on different sample spaces. It works like the Maya mesh transfer attributes. The add on lives in the Property panel under the mesh Data.
The Sample spaces are World, Local, Active UV and Topology. The mesh data includes: Shape (on the mesh or as a shape key) UV Vertex Groups Shape Keys
This tool is very useful for copying shape keys (blendshapes) between VRC avatar meshes.