e only. There is a distinction to make between open source and free software. While open source software is often provided free of charge, there are also many commercial open source prod- ucts. Furthermore, many closed source products are free (e.g. most of the Android apps and many "shareware" programs from the pre-mobile era). On the other hand, the term free software is also often used in the context of "freedom," as in "free speech" as opposed to "free beer," to indicate that the main idea of free software is freedom not only to use it as one likes, but also to modify and extend it. This distinction between free and open source was perhaps one of the earliest controversies in this area 6.3 Open Source (e.g. between Richard Stallman5 and Linus Torvalds6. Many other controversies followed, which however did not prevent open source projects from widespread adoption in servers, data centers, mobile phones, and many other appliances. To illustrate the importance of open source, below we provide a very incomplete list of some of the most widely adopted open source implementations: Linux kernel, which is also what Android is based on. Linux operating system (including the kernel and the GNU software suite), e.g. RedHat and Ubuntu, which are what many cloud and enterprise servers use. LAMP (Linux, Apache, MySQL, PHP/Perl/Python), which is what the vast majority of small to medium websites run on. FreeBSD operating system, significant parts of which also power Apple macOS, iOS, and Sony Playstation. Initially, the open source movement was primarily driven by volunteers; however, in recent years the vast majority of the open source code has been contributed by people employed by large corporations. Furthermore, while in the past the decision process was very much ad hoc (driven by community, with "maintainers" such as Linus Torvalds having the final decision power), it is now increasingly the case that the process is governed by organizations such as the Linux Foundation. Given the widespread adoption and huge success 