Linux is a UNIX like, POSIX compliant operating system distributed under the 

GNU software license. This means that the operating system can be distributed 

for free. Linux supports all the major window managers and all the Internet 

utilities, such as File Transfer Protocol (FTP), Telnet, and Serial Line Internet 

Protocol (SLIP). It provides 32 bit and 64 bit multitasking, virtual memory, shared 

libraries, and TCP/IP networking. It is coupled to a native POSIX thread library 

for high performance multithreading, symmetric multiprocessing (SMP) up to 16 

logical CPUs or eight hyperthreaded CPU pairs, and massive parallel processing 

(MPP) up to 10000 AMD Opteron processors in a new Cray computer under 

development. 

Linux has been developed to run on the x86, Itanium , AMD64, and IBM 

Eserver 

zSeries , iSeries , pSeries , and S/390  architectures. A common 

source code base is used for all of them.

1.6.1  Licensing

Linux is distributed under the GNU GPL agreement. The complete license 

agreement can be accessed at:

http://www.gnu.org

This section briefly summarizes the terms of this license:

Free redistribution of the software is allowed. There are no restrictions in 

regard to selling or giving away the software.

Modifications and derived works are to be distributed under the same terms 

as the original software.

Modified source code may have distribution restrictions. The license should 

explicitly allow the redistribution of derivative works. This 

cannot

 include the 

patched code, since patched code may not be considered derivative work.

The license does not discriminate against any person or group of persons.

The rights that are attached to the program, when the license is distributed, 

apply to all to whom the program is redistributed.

The license must not restrict other software that can be distributed along with 

the licensed software.

 Chapter 1. Introduction 

7