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.
The source code for the Linux kernel is hosted at kernel.org.
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.
There are several SQL servers available for Linux. You can get the source code for MySQL and PostgreSQL from their respective websites.
Distribution is a word usually used to refer to a certain version or "flavor" of UNIX or Linux, and open source is code that is free to modify and recompile, distributed in source code form (and usually precompiled binaries, as well). Most open source software is available free of charge, but not all of it. So an "open source distribution" would be a certain version of UNIX or Linux that is free to modify and recompile, distributed in source code form. All Linux distributions are required to be open source, as they are all under the GNU General Public License, which you may read at the following address: http://www.gnu.org/licenses/gpl.html
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.
Linux is referred to as "open-source" precisely because it is. Open-source is the ability for anyone to view the code necessary to make the program. The Linux kernel, and most of the programs that are available for it, have their source code available, under a variety of licenses.
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Linux Torvalds made the source code to the Linux kernel available because he wanted both for it to serve as a learning tool, and to convince people to work on it.
Students understand the source code for the operating system and how Linux works without complications.
Students understand the source code for the operating system and how Linux works without complications.
Unix is NOT open source, it is proprietary copyrighted code owned by AT&T and you must purchase a license to use it, as you do on Windows and Mac OS X.However both Linux and GNU are open source OSs with equivalent functionality to Unix.
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