1.5. Sources and Licenses
When you get Linux, you also get the source code. The same goes for all the utilities on Linux (unless your vendor offered a commercial application or library as a special enhancement). You may never bother looking at the source code, but it's key to Linux's strength. The source code has to be provided by the vendor, under the Linux license, and it permits those who are competent at such things to fix bugs, provide advice about the system's functioning, and submit improvements that benefit all of us. The license is the well-known General Public License, also known as the GPL or copyleft, invented and popularized by the Free Software Foundation.
The FSF, founded by Richard Stallman, is a phenomenon that many people would believe to be impossible if it did not exist. (The same goes for Linux, in fact -- 10 years ago, who would have imagined a robust operating system developed by collaborators over the Internet and made freely redistributable?) One of the most popular editors on Unix, GNU Emacs, comes from the FSF. So do gcc and g++ (C and C++ compilers), which for a while used to set the standard for optimization and fast code. One of the largest projects within GNU is the GNOME desktop, which already encompasses several useful general-purpose libraries, window managers, and applications. The GNOME developers have big plans for providing an environment that integrates not only the applications on each user's system but also the services provided throughout a whole organization.
Dedicated to the sharing of software, the FSF provides all its code and documentation on the Internet and allows anyone with a whim for enhancements to alter the source code. One of its projects is the Debian distribution of Linux.
In order to prevent hoarding, the FSF requires that the source code for all enhancements be distributed under the same GPL that it uses. This encourages individuals or companies to make improvements and share them with others. The only thing someone cannot do is add enhancements and then try to sell the product as commercial software -- that is, to withhold the source code. That would be taking advantage of the FSF and the users. You can find the GPL in any software covered by that license and online at http://www.gnu.org/copyleft/gpl.html.
As we said earlier, many tools on Linux come from BSD instead of GNU. BSD is also free software. The license is significantly different, but that doesn't have to concern you as a user. The effect of the difference is that companies are permitted to incorporate the software into their proprietary products, a practice that is severely limited by the GNU license.
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