Linux is an open source (free sofware) kernel developed by Linus Torvalds, and uses software tools developed by the GNU project to comprise an open source operating system. It mimics the Unix kernel, but was written from scratch with no proprietary code. Its development cycle has been relatively short (compared to the proprietary based Windows operating system) and is considered by some to be technically superior. Due to this, it has become the 'poster child' for the open source community (it stimulated the interest of Eric Raymond and the paper Cathedral and Bazaar) and free software in general. While it is commonly referred to as Linux, others refer to it as GNU/Linux (Richard Stallman) due to its reliance on other GNU software in order for it to function (more details here). Linux did prove to be the 'missing link' for the GNU project by providing a usable operating system kernel, which has been packaged into a complete free software operating system by other hackers and commercial distributors (principal commercial distributor: Red Hat). GNUs efforts in this regard (the GNU Hurd) are still on going. Linux has wide adoption in the much smaller server side operating system market. Its penetration on the client side (where windows is dominant) has been limited to the hacker community.