DragonFly belongs to the same class of operating systems as other BSD-derived systems and Linux. It is based on the same Unix ideals and APIs and shares ancestor code with other BSD operating systems. DragonFly is differentiated from other operating systems in its class by, among others, the HAMMER file system, Virtual Kernels, swapcache, and the pervasive use of soft token locks. DragonFly provides an opportunity for the BSD base to grow in an entirely different direction from the ones taken in the FreeBSD, NetBSD, and OpenBSD series.
The KoreLogic Expression Language Library (libklel) is a C library that provides a simple expression language that can be embedded in other programs. It does not implement a full programming language, but rather a simpler expression language called KL-EL that is designed to provide arithmetic and logic operations in situations where embedding a full programming language would be overkill. KL-EL can access functions and variables exported from the embedding program, and is statically and strongly typed, which helps ensure that expressions are valid before they are executed. The embedding API is easy to use, and the library itself is very small.