OSS License Types (Part 3 of 3) - Reciprocal Licenses

This third post in the license type series will review the category of licenses often referred to as having a reciprocal nature.

1. Permissive licenses
2. Corporate licenses
3. Reciprocal licenses

This group of licenses are called reciprocal because the licensee is usually required to adopt the license of the consumed component when creating and distributing any derivative works.  Since the terms of the licenses generally require full source code disclosure, the ramifications of such reciprocity should be carefully considered.  Sometimes we will see these licenses referred to as:

1.  "copyleft"  - a play on the IP term "copyright", or
2.  "viral"  - because they "infect" any larger bodies of work upon incorporation, or
3. "hereditary" - because once these reciprocal terms take hold on a project they are passed down through the progeny of the software line

Common examples include:

1. GPL (all versions) - GNU General Public License
2. LGPL - Lesser General Public License - this one is a little less onerous from a compliance perspective
3. AGPL - Affero GPL
4. OSL - Open Software License

Downstream reciprocity requirements imposed by these licenses require very careful use case analysis when contemplated in a commercial context to ensure business goals align with any required source code disclosures.  Special attention must be directed to the definitions of derivative and collective works since the licenses themselves do not always use the generally accepted terms or definitions as established by copyright law.  In addition, reciprocity is often triggered by distribution which is not always clearly defined by the terms of the license itself.  There are a handful of reported interpretations by various courts which are somewhat informative and will be the subject of another post.

In summary, advising clients on the use of OSS components subject to this category of licenses requires careful scrutiny of both the applicable license terms and the business intent driving a proposed use case.  These licenses do serve a particular purpose within the broader market but must be approached with caution in order to avoid undesirable consequences.