BSD
The BSD family used to be the reference for Unix-like OSes. Since then, the standard has become POSIX, and 4.4BSD has split into lots of diverging projects:- DragonFlyBSD - A Unix-like OS of the BSD family
- FreeBSD - FreeBSD (a successor of 386BSD) is a Unix-like OS, mostly for the Intel and Alpha platforms and is most up-to-date among BSDs regarding device drivers
- Lites - Lites is a Unix-like OS of the BSD family as a "singleserver" over the Mach microkernel
- NetBSD - NetBSD is a Unix-like OS of the BSD family which focuses on portability and networking and supports tens of platforms
- OpenBSD - OpenBSD is a Unix-like OS of the BSD family, has split from NetBSD, and focuses on stability and security
- TrustedBSD - A Unix-like OS of the BSD family which provides a set of trusted operating system extensions to the FreeBSD operating system, targeting the Common Criteria for Information Technology Security Evaluation (CC)
They all seem to have some binary compatibility with Linux, at least on the i386 platform.
Pages in this topic: DragonFlyBSD FreeBSD Lites NetBSD OpenBSD TrustedBSD
Also linked from: DOS KallistiOS Mac OS X Mach MachTen Microkernel Microkernel Debate OS161