Introduction to Red Hat Linux and the General Public License

The GNU GPL was developed in the 1980s by Richard Stallman, an advocate of free software who eventually founded the Free Software Foundation (FSF).
Stallman used the concept of copyleft to protect the freedom of GNU project software, effectively reversing the use of copyright law to ensure that source code was never closed off.
Copyright is a general method for making a program or other work free, and requiring all modified and extended versions of the program to be free as well.
This early effort to secure freedom in distributing and viewing the source code has led to the popular OSS initiative.

A software license is a legal instrument (usually by way of contract law, with or without printed material) governing the use or redistribution of software. Under United States copyright law all software is copyright protected, except material in the public domain. A typical software license grants an end-user permission to use one or more copies of software in ways where such a use would otherwise potentially constitute copyright infringement of the software owner's exclusive rights under copyright law.
In addition to granting rights and imposing restrictions on the use of software, software licenses typically contain provisions which allocate liability and responsibility between the parties entering into the license agreement. In enterprise and commercial software transactions these terms, such as limitations of liability, warranties and warranty disclaimers, and indemnity if the software infringes intellectual property rights of others.
An IT professional who has earned the Red Hat Certified System Administrator (RHCSA) is able to perform the core system administration skills required in Red Hat Enterprise Linux environments. The credential is earned after successfully passing the Red Hat Certified System Administrator (RHCSA) Exam (EX200).