Viral license

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A viral license is a term used to describe a license that allows derivative works only when licensed identically to the original. Such licenses exhibit a viral phenomenon as they spread from work to work. It is generally used to distinguish copyleft licenses^{[by whom?]}, such as the GNU General Public License (GPL), from more permissive licenses, such as the BSD license, which allow more choices for licensing derivative works.

• 1 Scope
• 2 History
• 3 Criticism of the term
• 4 Interoperability
• 5 See also
• 6 References

Scope

The term is most often used to describe the GPL,^[1] which requires that any derivative work also be licensed with the GPL. This applies even if only a small amount of GPL code is used in the derivative work.^[1] Thus the GPL is referred to as a viral license because the original GPL product "infects" the derived work by forcing it to also be licensed under the GPL.^[1] This intention is not denied by the GPL authors who have written the license with exactly this goal and are sure that propagation of the GPL has a positive effect. However, this can lead to problems when software is derived from two or more sources having incompatible viral licenses. In this case, the derivative work cannot be re-licensed at all.

Although the term viral license is generally associated with licenses that promote free content, many proprietary licenses also have viral characteristics. For example, original equipment manufacturer source code software distribution agreements generally grant licensees the right to redistribute copies of the software, but restrict what terms can be in the end user license agreement.^[2] However, derivative work is much less common with proprietary licensed work and so the viral phenomenon is not as evident.

In addition any Creative Commons license that includes the Share-alike clause can also be considered to be a viral license. And therefore it follows that Wikipedia is itself licensed under a viral license.

For example when it was revealed that French author Michel Houellebecq plagiarized sections of wikipedia articles in his novel La Carte et Le Territoire, some commentators said that this automatically made his entire book licensed under Creative Commons license. [1]

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