Hurd vs Plan9 vs Linux vs eCos vs FreeRTOS what are the main differences specially with Hurd?

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http://unix.stackexchange.com – Hurd is actually not Unix nor Linux. But more superior says. Where Plan9 and Linux are in the range of Unix/Linux. eCos and FreeRTOS is also completely not unix/linux. What is the main differences between Hurd and FreeRTOS/eCos and General Unix/Linux? Can i name FreeRTOS or eCos tree as Hurd family? As those OS are not considered to be Linux nor Unix. (HowTos)