Unfortunately, they haven't been updated in a while. But this is what we mean when we want docker on other hosts. use FreeBSD's native jail and linux subsystems. In other words, "OS-level virtualization" 
Rather than treating other platforms like second class citizens and relying on ad-hoc workarounds that require virtualbox, a middleman linux distribution running in the background; not to mention the error-prone networking redirection the aforementioned introduces.
1. The whole point of docker is to not have to haul in a linux distribution and a fire up a vm just to deploy something for development or production. If they're using Docker w/ a VM, they're better off just using Vagrant.
2. FreeBSD jails work fantastic. What's keeping docker from abstracting upon that and supporting it officially, especially seeing these two implementations in the wild?
I look forward to seeing more of kvasdopil's docker fork (https://www.freshports.org/sysutils/docker-freebsd/) and jetpack.
Warning: I have not yet tested this yet, but it's about the same way as it works on macOS.
Also, I would have probably tried to use boot2docker  as guest instead of Alpine.
 https://www.freshports.org/sysutils/docker/ (< you probably have to build it yourself)
I didn't notice the docker client was in the ports tree. I may have to give this a go later this week.
EDIT: we have an openbsd developer on the team that built LinuxKit and Docker for Mac, so we should be able to help fix any issues...
So if I run Docker in a Linux VM on OpenBSD, I don't think it counts as "Docker on OpenBSD", IMHO.
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. :-)
The naming convention is consistent, if a bit strange.
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.
Sadly, no Broadcom support :-(
It uses the urtwn driver in OpenBSD and FreeBSD. It works...ok. Super small and a handy built in blue-LED so you know when it's powered and connected. I tend to leave it plugged in even when I reboot into macOS because it's pretty much ignored there due to lack of out of box macOS kernel module I believe.