Introducing OpenLinux 6 Getting Started Guide provide for inclusion of source code with its associated software, but to date the GPL is the most common Open Source license. NOTE: Programs that run on Linux don’t have to be licensed under the GPL or any other Open Source license. Thousands of commercial applications that you can run on Linux (such as Corel WordPerfect 8 or Oracle 8 Server) use commercial licenses; they are not “GPLed,” and do not include source code, thus they cannot be freely distributed. The Linux product you have purchased is built upon the work of thousands of individuals, then assembled and packaged by Caldera Systems, Inc. More com- plete histories of Linux and the free software and Open Source development communities are available in many of the online and printed resources named at the end of this chapter. How is Linux Used? Today, Linux is first and foremost a server operating system. Although many applications are now appearing that allow Linux to be used as a primary worksta- tion or desktop system, most users of Linux focus on the server capabilities of the operating system. Some of the reasons that Linux makes a very strong server include: • High performance. Linux performs as well as (if not better than) other operating systems running on identical hardware. • Security. Alerts to any possible security holes and patches to fix the prob- lem are immediately distributed. No need to wait for months while a ven- dor creates a fix. • Good value. While Linux can be downloaded free of charge, even the commercial products such as OpenLinux 2.3, which include documenta- tion and the support of a stable commercial entity, are still tremendous values compared with other operating systems. So how, specifically, is Linux used? The following list shows the most popular uses of Linux. (Basic configuration information for each of these uses, plus some others, is given briefly in Chapter 12 of this manual). • Web server • FTP server • Email server