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BeOS



BeOS: a freely available operating system.

(related variations: BeOS OpenBeOS Haiku)
BeOS is not much like UNIX, making it nearly unique in this list. While traditional BeOS is also commercial and cannot be freely downloaded, there have been recent efforts to make a BeOS work-alike called variously OpenBeOS and Haiku. Traditional BeOS supports PowerPC and x86., but Haiku currently supports only x86