No it is not built on the same platform, Linux was a "from the ground up" rewrite of a Unix Kernal by Linus Torvalds he did it as a personal project and released it free to the world to upgrade, it was such a good implementation of the ideals of Unix that it won great favour amongst the developer community.
Few people remember that Unix in those days (I mean the early 1990's) was extremely fragmented, there were many implementations including extremely cheap versions like Coherent and even Sco Unix could be got for acceptable money. IBM AIX was another matter and IBM were big with the IBM AS400 OS as an alternative midrange OS (somewhere between the mainframe and micro) in those days.
Linux is impressive, personally I make a living from Windows (wind woes
) and Windows 7 is a very advanced OS and a big big improvement on Vista, personally my view is that you have to treat W7 really badly to get a big mess or disaster on your hands now, still happens but it's rare, it's a good OS.
Linux is not immune from disasters either but at least it's free for many good distros