Linux is the first truly free Unix-like operating system. The underlying GNU Project was launched in 1983 by Richard Stallman originally to develop a Unix-compatible operating system called GNU, intended to be entirely free software. Many programs and utilities were contributed by developers around the world, and by 1991 most of the components of the system were ready.

"The GNU operating system is a complete free software system, upward-compatible with Unix. GNU stands for “GNU's Not Unix”. Richard Stallman made the Initial Announcement of the GNU Project in September 1983. A longer version called the GNU Manifesto was published in September 1985 [...] By 1990 we had either found or written all the major components except one—the kernel.

If you look at the Free Software scene you see that most if not all projects - at the operating system level and at the application level - and magazines, blogs and newspapers concentrate on GNU/Linux. Also you can note that most people start with a Linux distribution and then lock himself in the GNU/Linux world.

I’ve pretty much assumed that technologically speaking, if Windows has it, Unix and the like must also have the same functionality. As I re-engage with Unix and Linux developers and IT professionals in recent months, though, I can see that there are some areas – particularly in security - where Windows is far ahead of the *x operating systems. Here’s a few...

For the last 40 years, Unix operating systems have helped to power mission-critical IT operations around the globe. Now, as Unix enters middle age, its backers are busily developing the new specifications that they hope will carry the OS forward into the next age of computing

KDE now provides an easy to use contemporary desktop environment available for UNIX and compatible systems. Together with a free implementation of UNIX such as GNU/Linux, UNIX/KDE constitutes a completely free and open computing platform available to anyone free of charge.

"A brief review of the history of Unix will place in context much of the terminology and philosophy of this operating system. Terms like Linux, GNU, Unix, Gnome, Free Software, and Free and Open Source Software get bandied around, often with little understanding and usually with much misunderstanding..."

We are very familiar with Linux and its relation with UNIX.But most us of dont actually know what are differnces between the two.
Linux is called Unix-like and is not a true Unix operating system.

Anti-virus software has become a critical aspect of computing at all levels. Although to this point it seems the only operating system that is really targeted by viruses is Microsoft Windows, the time will come when UNIX-based operating systems will be equally as marked.