I wonder if we'll see a move towards getting Docker working on FreeBSD using either Jails or bhyve finally, since it talks about using bhyve hypervisor... That would be really great.
It should be possible to build a simpler port for FreeBSD with the recent Docker 1.11 release. It moved the container execution to containerd (https://github.com/docker/containerd), so that's where a bunch of the Jails logic would go.
I'm quite keen to see Docker running on FreeBSD so I can use it for my CI pipelines. I'm less interested in Linux emulation to run Linux images -- I'd like Docker support on FreeBSD to run FreeBSD images first!
Can't speak for anyone else, but while I think jails are "better" for a variety of reasons it seems clear there is far more market momentum behind Docker. More particularly, its toolchain. Given the choice between building myself (or relying upon a small, but talented, pool of devs) and drafting off tens of millions in VC cash and a much larger community I think some would prefer the ability to have a *BSD CI chain that is just a config setting in a Docker setup.
Containerd is just one part of what Docker does. There is also image management (signing via Notary), distribution (pull/push to the Hub), orchestration (Swarm and friends), linked services (Compose), etc. You could reuse all the rest of it while running containers in FreeBSD jails as the method of containment.
