It works with leveraging vCenter 6 vAPI. vCenter 6 is the first vCenter version providing a public API for tagging. Earlier versions only supported PowerCLI commandlets or private APIs (that James reverse engineered here : Native vRO vCenter Tagging - No Powershell).
It can be used with vRealize Automation "Anything as a service" (For example attaching a tag to an object that would enable a given service).
The workflows are not checking if you attach a particular object type to a tag that has a parent category not supporting it.
The install workflow may fail to delete the resource element that were imported. It is not affecting the plug-in functionality but may affect a future upgrade. I have a bug opened about this with engineering. You can delete these resource elements with renaming them in the vCO client and deleting them.
I only tested it with vRO 6 + vCenter 6 (since vCenter 6 is required and since passing vCenter objects to the plug-in is likely a requirement if you need to tag vCenter objects).
Use at your own risk. I made this as a first step to learn how to use vAPI and provide native vCenter tag orchestration.