Chapter 2. Free Software and Open Source

Viruses and Freedoms

The first thing any lawyer learns about open source is that there are two kinds of open source licenses: "viral" and "nonviral."

When lawyers use the term "viral," they are referring to a license condition that requires the licensee to redistribute source code in outbound licenses only on the same terms as the inbound license. Although many find this a difficult concept, it is not fundamentally different from licensing conditions common in proprietary software licensing—a paradigm with which most licensing lawyers and businesspeople are quite familiar.

Consider, for example, the typical original equipment manufacturer (OEM) source code software distribution agreement. Such an agreement typically grants the OEM licensee the right to redistribute copies of software, subject to certain flow-down provisions that restrict the terms on which the OEM may grant end user licenses. Exhibit 2.1 shows some similarities and differences between a viral license agreement and an OEM source code license agreement.

Thus, the flow–down provisions of the GNU General Public License (GPL), in scope and structure, are not unlike those of OEM contracts that have been used in the software business for many years.

Terminology in this area is fraught with peril. The term "viral" is a pejorative term that is not well received by software developers. In addition, the term "viral" is imprecise, because sometimes it is used to refer only to the GNU General ...

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