I wish it wasn't necessary to use a VM to run Docker on a Mac. Shouldn't it be easy to get Jails running on OSX, and wouldn't that be a good basis for Docker? (I'm not sure.)
You still have the issue of not having an implementation of an Ethernet or network virtualisation features like Crossbow/VImage.
Even if you were to solve that you would be stuck with the VFS graph driver unless you could get a CoW filesystem up and running on OSX (maybe revamp the old ZFS port?).
Docker is much more than just jailing is basically the problem.
Well first of all Apple has shown no interest in adding jails to osx. Second, there is not yet a proof of concept implementation of Docker using jails (there are significant differences between the implementation of jails and Linux namespacing). Third, you need a filesystem like zfs, but Apple does not support that. Fourth, all Docker code currently being distributed is for Linux/amd64.
Implementing it on FreeBSD would be immensely easier as a first step.
