Unlike Microsoft Windows, you don't need a license to download, use, copy or give away Linux or the many distributions associated with it. Linux is actually the kernel (the heart) from which many distributions of open source operating systems radiate outwards. Ubuntu, Linux Mint, are just two of many popular operating systems that are entirely free.
The Linux kernel is released under the GNU General Public License version 2.
GPL
Linux is not illegal. Linux is a free, public license software modeled on Unix.
Version 2 of the General Public License.
You do not need a license to edit Linux's source code. The GPL applies only to how you distribute it. End users do not license Linux in any way for use or modification, they're allowed to do anything they like, so long as if they try to redistribute the result they do so under the terms of the GPL.
Completely free. If someone sells you Linux, it is legitimate, however, it will not be for a license to use the software. The GPL is not that kind of license. However, it is still free as in freedom, not free as in beer, meaning it is entirely valid under the GPL to sell Linux.
Nothing. The GPL is not a license you purchase. It is legal to sell Linux distributions, but most (Except for Red Hat Enterprise and a few others.) don't cost a thing and are free to download.
Most people still don't know what Linux is, so it'd be difficult to say that it is "famous." Linux has grown in notoriety due mainly to the open nature that it is developed under. Anyone can contribute code towards Linux, and anyone can use Linux in their own projects, as long as they obey the terms of the license.
One can find a laptop with Linux at any available online seller. In fact almost all laptops have Linux and in some cases buyers choose to pay a license for Windows. Best places to find laptops with Linux are Amazon, Best Buy and Overstock.
Microsoft and Linux have no direct relationship. Microsoft has frequently attacked the reliability and cost effectiveness of Linux in order to promote their own Windows Server products. They do not release any software for Linux directly, but have made several "deals" with various commercial Linux vendors, such as Novell, Xandros, and Linspire, to license Windows media codecs.
Many embedded devices incorporate Linux, and those are proprietary products. But the Linux license (GPL) requires that the distributor also make the source code available, including any modifications they may have made to the operating system.
The short answer is that Linux is a computer operating system, and is an alternative to older products such as DOS, Windows, MacOS or UNIX. The way that Linux is written and distributed is new and revolutionary - it is maintained by an open community of programmers and you can get it for free. This has created a growing industry of distributors who bundle Linux and other useful stuff into a distribution package or distro, to make life easy for the end user. This method of development and distribution is protected by an equally revolutionary license, the GNU Public License
The open source model allows the freedom for anyone to view, modify, and distribute source code. The Linux kernel and the many distributions that uses it are released under any given open-source license which allows anyone to build their own Linux distribution at will.
Linux is the best operating system in the world, Linux is Open Source, Secure, Stable, License Free and also multi platform supported OS and shipped with thousands of FREE applications.