Gentoo is a free operating system based on either Linux or FreeBSD that can be automatically optimized and customized for just about any application or need. Extreme configurability, performance and a
... [More] top-notch user and developer community are all hallmarks of the Gentoo experience. [Less]
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]
The AROS Research Operating System is a lightweight, efficient and flexible desktop operating system, designed to help you make the most of your computer. It's an independent, portable and free
... [More] project, aiming at being compatible with AmigaOS 3.1 at the API level (like Wine, unlike UAE), while improving on it in many areas.
The source code is available under an open source license, which allows anyone to freely improve upon it. [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).