Not at all. I’m in the process of making that clear in documentation: openHABian is (1) an image for the Raspberry Pi and (2) the script collection inside it which can be used on other Debian/Ubuntu based systems.
So yes, you should be able to use openHABian on your Pine64. After installing your base system, here is what you need to do:
# install git
sudo apt-get update
sudo apt-get install git
# get openHABian
cd /opt
sudo git clone https://github.com/ThomDietrich/openhabian.git
cd openhabian
# Execute as root
sudo /opt/openhabian/openhabian-setup.sh
In the menu presented, just execute the first few steps. let me know of any errors presented in the console. If you see a problem, please let me know so I can fix it in the script.