No, it's not. It has nothing to do with linux at all.
Again, no. No part of the linux system or the GNU tools are implemented in ReactOS.
From the website:
" ReactOS is a free and open-sourced operating system based on the Windows NT architecture, providing support for existing applications and drivers, and an alternative to the current dominant consumer operating system.
It would be perhaps important to start by saying what ReactOS -isn't-. It is not another wrapper built on Linux, like WINE. "
Basically, it's an attempt to make a windows clone that is free and open source. It is legal, there was a code freeze for 2 years previously to make sure no part of the windows code/system was copied and used within it. It's cool in a vm to try, but it's nothing special. I've had better luck running programs via Wine in linux. It's also good for general research on windows systems since it maintains the FOSS model. But to use on a day to day basis? Not even close.
Lastly,
The? There's hundreds of Linux OS's out there. Don't try one and judge them all the same. There are significant differences and goals with each one.