FreeBSD is an advanced operating system for x86 compatible (including Pentium and Athlon), amd64 compatible (including Opteron, Athlon64, and EM64T), UltraSPARC, IA-64, PC-98 and ARM architectures. It
... [More] is derived from BSD, the version of UNIX developed at the University of California, Berkeley. It is developed and maintained by a large team of individuals. Additional platforms are in various stages of development. [Less]
NetBSD is a free, secure, and highly portable Unix-like Open Source operating system available for many platforms, from 64-bit Opteron machines and desktop systems to handheld and embedded devices.
... [More] Its clean design and advanced features make it excellent in both production and research environments, and it is user-supported with complete source. Many applications are easily available through pkgsrc, the NetBSD Packages Collection. [Less]
PLD is a free, RPM-based Linux distribution, aimed at the more advanced users and administrators, who accept the tradeoffs of using a system, that might require manual tweaking in exchange for much
... [More] flexibility. Simultaneous support for a wide variety of architectures and non-conservative approach to RPM usage provides our users with a consistent environment on almost all available architectures. [Less]
The HelenOS project is an effort to develop a complete and usable modern operating system, yet offering room for experimenting and research. HelenOS uses its own microkernel written from scratch and
... [More] supports SMP, multitasking and multithreading on both 32-bit and 64-bit, little-endian and big-endian processor architectures, among which are AMD64/EM64T (x86-64), ARM, IA-32, IA-64 (Itanium), 32-bit MIPS, 32-bit PowerPC, SPARC V9 and Xen 3.0. Thanks to the relatively high number of supported architectures and suitable design, HelenOS is extremely-well portable. [Less]
AuroraUX is an operating system distribution based on the OpenSolaris kernel source base. The goal of the AuroraUX project is to create a high reliability core operating system using the US Department
... [More] of Defense-developed Ada programming language. While it is meant to be minimalistic and used as a base for other distributions, it will also be functional as an operating system in itself.
#auroraux @ irc.freenode.net [Less]
PM2 is a low level generic runtime system which integrates multithreading management (Marcel) and a high performance multi-cluster communication library (Madeleine).
MidnightBSD is a desktop operating system for ia32 and amd64/emt64 computers. It uses GNUstep and related software to provide an easy to use environment.