AFAIK, Richard Stallman is the brains behind both. He founded the gnu projects, they worked away at the various smaller programs all released under the gpl (= copyleft), which are free and gratis for us to use. Then they went the wrong way on the design choices in the kernel; They went for a micro kernel which has huge problems letting the left hand know what the right hand is doing, and had their system completed by Linus Torvalds who wrote his own monolithic kernel. Linux was born, but it's over 90% gnu.
This is all well documented online. Look it up. All the search terms you need are up there.