I spent a few hours this week creating a FreeBSD port for Drone, only to find out that the OSS version of Drone doesn't support external workers and since FreeBSD doesn't do Docker, Drone is pretty much useless on FreeBSD. It would be great if it was mentioned in their documentation so I didn't waste my time with Drone, but it's not.
Concourse on the other hand seems to work on FreeBSD and doesn't have artificial limits to try and sell something.