What is that?
There is a repository that publishes it, and in fact, it is the same container IRIS Community Edition containers you have on official InterSystems listing which have the pre-loaded ObjectScript Package Manager (ZPM) client.
So if you run this container with IRIS CE or IRIC CE for Health you can immediately start using ZPM and install packages from Community Registry or any others.
It's really handy if you want to test a new interesting ZPM package and not harm any of your systems.
Suppose, you have docker-desktop installed. Pull the image: