DragonFly BSD is a fork of FreeBSD 4.8 (June of 2003, by Matthew Dillon). It is based on the same class of operating system as BSD and Linux, but it takes a different direction from the FreeBSD, NetBSD and OpenBSD series.
The DragonFly project focuses on rewriting most of the major kernel subsystems with a great deal of work in nearly every subsystem, particularly the filsystem APIs and kernel core. The DragonFly project provides native clustering support in the kernel.
In 2007, a new filesystem called HAMMER was developed for DragonFly. This filesystem has been designed to solve numerous issues and to add many new capabilities to DragonFly, such as fine-grained snapshots, instant crash recovery, and near real-time mirroring. The filesystem is also intended to serve as a basis for the clustering work that makes up the second phase of the project.
The most recent release is DragonFly BSD 4.6, released in August 2016. The following release notes from dragonflybsd.org provides an overview of the most recent changes:
DragonFly version 4.6 brings more updates to accelerated video for both i915 and radeon users, home-grown support for NVMe controllers, preliminary EFI support, improvements in SMP and networking performance under heavy load, and a full range of binary packages. 4.6.1 adds some security fixes and a power management daemon.