Free and open source development models have made tremendous contributions to computing, sustaining both research and commercial projects and making it easier for large groups of people, who may not even be acquainted, to help each other. While this growing activity has a promising future, all of this work is built on top of licenses—legal documents—that often seem arcane or difficult to understand. Businesses and individuals aren’t always sure what is at stake in their decisions to participate, and deciding which license to use for a particular project can be a project of its own.

This book is designed to simplify those decisions, explaining the different licenses and their effects on projects, including both commercial and non-commercial projects. It explores how licenses can be used as glue to bind groups of people together in common, and how the different styles of license interact with different kinds of projects.

The licenses and projects covered include:

  • MIT

  • BSD

  • Apache, Versions 1.0 and 2.0

  • Academic Free License (AFL)

  • GNU General Public License (GPL)

  • GNU Lesser General Public License (LGPL)

  • Mozilla Public License (MPL)

  • Qt License

  • Artistic License

  • Creative Commons Licenses

  • Sun Community Source License and Commercial Use Supplement

  • Microsoft Shared Source Initiative

Each license is examined clause by clause, including both the original license text and explanation. This book also looks at issues affecting all of these licenses, including the formation of a contract, enforceability of warranty and other disclaimers, and cross-licensing.


A few lawyers will undoubtedly read this book, and hopefully find it useful, but you don’t need to be a lawyer to read this book. Whether you’re a programmer deciding what license to use in publishing a personal code library, a manager deciding if and how you can use open source code in your business, or a lawyer evaluating rules for integrating open source code with proprietary code, you should find the information you need here.


This book starts with the basics of contracts and licensing, proceeds through the details of the licenses, and concludes with a discussion of the implications of these licenses for organizations and for projects. You don’t need to read the book from start to finish, and it’s quite reasonable in some cases to read only the parts that apply to the licenses that interest you. This book has seven chapters:

Chapter 1, Open Source Licensing, Contract, and Copyright Law

This chapter takes a look at the traditional foundations below open source licensing, including contracts and copyrights, with a brief look at patents and warranties.

Chapter 2, The MIT, BSD, Apache, and Academic Free Licenses

This chapter takes a close look at licenses that specify terms, which allow the redistribution of source code but place few limits on its commercial use.

Chapter 3, The GPL, LGPL, and Mozilla Licenses

These licenses specify terms that are designed to keep source code and derivations of that code openly available for further community development.

Chapter 4, Qt, Artistic, and Creative Commons Licenses

This chapter looks at some licenses that take their own paths, reserving rights to the creator of a project, and, in the case of Creative Commons, licensing content that isn’t necessarily code.

Chapter 5, Non-Open Source Licenses

While free and open source licenses are the focus of this book, understanding proprietary licenses can also be important, especially as companies like Sun and Microsoft work on approaches that reserve many of their rights while attempting to reap some of the benefits of more open development models.

Chapter 6, Legal Impacts of Open Source and Free Software Licensing

Using or publishing software under a license creates obligations. This chapter examines how those obligations work and what their consequences may be, as well as questions of mixing licenses or publishing software under multiple licenses.

Chapter 7, Software Development Using Open Source and Free Software Licenses

The licenses are important, but their use makes them valuable. This chapter looks at how these licenses have been used and are being used on software projects, as well as how to choose from the many licenses available and what to do if you feel you must draft your own license.

Appendix A, Creative Commons Attribution-NoDerivs License

The Appendix contains the Creative Commons Attribution-NoDerivs 2.0 License, which sets terms under which this book may be freely distributed.

If you want to get an overview of all of the options in free and open source licensing and development, then it probably makes sense to read the book straight through. If you just want to look up a few licenses, it may make sense to pick up foundations in Chapter 1 and read the relevant sections in Chapter 2 through Chapter 5, and then look over Chapter 6 and Chapter 7.

Conventions Used in This Book

The following typographical conventions are used in this book:

Plain text

Indicates menu titles, menu options, menu buttons, and keyboard accelerators (such as Alt and Ctrl).


Indicates new terms, URLs, email addresses, filenames, file extensions, pathnames, directories, and Unix utilities.

Indented quotations

Indicate the text of the original licenses and separate them from the commentary.


This icon signifies a tip, suggestion, or general note.


This icon indicates a warning or caution.

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I want to thank my editor, Simon St.Laurent, without whom this book would never have been written; Eben Moglen, who introduced me to open source and free software; and Mitchell Baker, Danese Cooper, David Stutz, and John Cowan for their invaluable help in reviewing and correcting this book. I also want to thank John Urda, for his help and encouragement; and Jason Yung, for his last-minute assistance. All the mistakes remain the property of the author.

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