Installing Docker on a Pi is super easy also.
First make sure your Raspian is up to date
sudo apt-get update
Then, all you need to do is run this.
curl -sSL https://get.docker.com | sudo sh
And voila, docker is installed:
pi@raspian:~$ docker info
Now, you can run my Mystic BBS image or my MBSE BBS image. If you need some more info about Docker, you might find this useful.