There once was someone who was running on FreeBSD many many years ago. I’ve not heard anything about running on any BSD system since then. BSD isn’t a supported platform so you would likely be on your own for installation, setup, and configuration. You won’t find a package unless someone created one in secret.
But it should work. You’ll just have to do a manual install. You’ll need to install a Java 11 runtime and then follow the manual installation instructions under the Linux installation page, replacing the Linux standard paths and commands with the OpenBSD paths and commands. You’ll have to write and configure the service start script yourself since I’m pretty certain systemd isn’t on OpenBSD.
You’ll be largely on your own for installation and hardware access type issues. No one here I know of is trying to run on a BSD.
Maybe they were running it on FreeBSD because it supports docker. I dont think OpenBSD supports docker.
And yes you are right, systemd isn’t a thing in OpenBSD.
Either way thanks, will give it a try on the weekend.