Linux in a Nutshell, Fourth Edition

Sources and Licenses

Some distributions contain the source code for Linux; it is also easily available for download at http://www.kernel.org and elsewhere. Source code is similarly available for all the utilities on Linux (unless your vendor offers 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. Under the Linux license, the source code has to be provided by the vendor, 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 everyone. The license is the GNU project’s 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 might believe to be impossible if it did not exist. (The same goes for Linux, in fact—15 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 set the standard in the industry for optimization and fast code. One of the largest projects within GNU is the GNOME desktop, which encompasses several useful general-purpose libraries and applications that use these libraries to provide consistent behavior and interoperability. ...