Open Source Operating Systems

• Croquet@
• Erlang@
• FreeBSD@
• Linux@
• Mach@
• Oberon@

• Open Firmware@
• OpenBSD@
• Squeak@
• TUNES@
• VMS@

• Computers: Open Source 
• Computers: Programming: Languages: Open Source 

• Celadon Reef  - Offers a code that controls the operation of open source and custom software to provide voice, video and data services.
• Free Linux CD Project  - Intends to bring Linux or any other *nix software to any user, free of charge. Includes donations information and brief overview.
• FreeOS.com  - Promotes free operating software. Contains articles, downloads and comparisons to various free OSs.
• GeckOS/A65  - 6502 Multitasking operating system and implements some Unix-like features. Plus download, description and development.
• Kernel.net  - Aggregates news, reviews and tutorials about open source software and features original articles about Linux.
• MacPorts  - Provides MacOS X simple way to install open source software products, under BSD license.
• Tester Tools  - Collection of free and commercial scripts and software.