(Full disclosure, I'm the author of the Medium post.)

It's essentially the way Docker for Mac works, though Docker for Mac has far more mature tooling these days. Before the switch to macOS's native Hypervisor.framework, it was very much running VirtualBox with a Linux VM as a "shim" if you will.

For local dev work it scratches an itch for me and maybe for the minority of folks wanting to use OpenBSD as their workstation OS. ("There are dozens of us. Dozens!")

Plus it's just fun to play with VMM. :-)

I read through the post, and thought, "Hold on, this isn't docker on OpenBSD, this is using OpenBSD's VM subsystem. Which is cool, but mostly unrelated to the title of the article."

The article is well written, but the title is kind of click bait. Why wouldn't you expect Docker (or any linux app for that matter) to run on a virtualization subsystem?

This would be similar to somebody getting Windows to run on vmm, and then writing an article, "Adobe Photoshop on OpenBSD"

Still a great article though. Recommended.

I'd wager their traffic is 1-2 orders of magnitude higher with this title than it would be otherwise. A while ago I did a bunch of work using Packer. I had encountered all sorts of interesting virtualization / networking / OS issues in the course of that work. But out of all that I wrote one blog post basically just saying I had started using the Docker builder in addition to what I was doing before. Most read blog post I've ever been involved with, by several landslides. It got picked up by several Docker bots on Twitter and retweeted by hundreds of people. Zero interesting technical content.