Chapter 15. O

Open source

Open source licenses are the agreements that make free and open source software feasible. Open source licenses usually allow any entity developing software to use them as long as they follow certain rules, from one person developing simple PC games for fun to a big development studio developing and maintaining a complex and popular operating system. An open source license exists to say, “You may use this software code and make modifications to it without paying for it or directly asking for permission, but only under these terms.”

There are lots of different open source licenses; some of the most common are the GNU Public License, BSD License, MIT License, and Apache License. As noted in Understanding Open Source and Free Software Licensing by Andrew M. St. Laurent (O’Reilly), open source licenses differ, but their terms usually include at least some of the following:

  • You must include a copy of the text of the open source license in your application or script’s code (usually done using code commenting).

  • You must not sell your software for any amount of money whatsoever. In the 1980s and 1990s, it was generally acceptable to pay for the materials cost of a floppy disk or optical disc, but not for the software itself. Now that open source software is distributed through the internet, no money should change hands. (Large corporations in the open source software business, like Red Hat, often sell customer ...

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