One of the oldest distributions of Linux, Debian GNU/Linux has an awesome reputation. At the heart of this distribution is a faithful community of programmers, all dedicated to advancing free software. More here
This is the purest in the sense of noncommercial and most stable flavor of Linux because all base components are community created, community supported, and no-strings-attached free. There are over 500 developers working together from around the world to put out the latest version.