November 8, 2018

A Quick Note on SSPLv1 pushing the same limit for very different reasons

Many readers will have seen MongoDB’s announcement of the Server Side Public License, Version 1, a new copyleft license written for MongoDB. SSPLv1 is based on AGPLv3, the Free Software Foundation’s network-copyleft license. MongoDB Inc. has submitted SSPLv1 to the Open Source Initiative for review.

Commentators have drawn comparisons to the License Zero Reciprocal Public License (L0-R), predecessor to the Parity Public License, one of the two public licenses developers can use through License Zero. I submitted L0-R to the OSI last year.

Parity and SSPLv1 both push the boundaries of copyleft in open source licensing. Both require sharing back more code in more situations than AGPLv3, OSL 3.0, or even RPL 1.5. Both were drafted with business needs in mind.

Parity and SSPLv1 differ in a number of ways, but most importantly in when their copyleft terms apply. Parity requires contributing code back in all cases that GPLv3 and AGPLv3 do, and then some. SSPLv1 requires sharing code in many cases that AGPLv3 does not, but does not require sharing code in many cases that AGPLv3 does. SSPLv1 is a strong copyleft license, but also a selective copyleft license, while Parity is a consistently strong copyleft license.

Those who favor Parity and those who favor SSPLv1 share a common interest. Both want open source copyleft to require sharing more code back, and in more situations, than it has under licenses like AGPLv3. In other words, both want to strengthen open source copyleft. But SSPLv1 and Parity address fundamentally different use cases.

SSPLv1 is very specifically tailored for network application projects, especially databases, developed by companies that make money selling hosting and related business services. The business intent of the license is to allow integration of network applications into broader applications, like web applications, without any requirement to share code back. That affords ease of adoption, the major business benefit of permissive licenses. At the same time, SSPLv1 requires others who host or provide other business services with the network application to share the source for management, logging, and other software used to do so. SSPLv1 uses copyleft to protect the paid service business model that release of the software, as a loss leader, leads towards.

Parity also supports business models, especially dual licensing. When getting patches back from users is key, Parity also works well. Finally, for those who believe all software ought to be free or open source, and find existing activist licenses like the GPLs insufficient or compromised, Parity provides the strongest-available, consistent copyleft option, in much shorter and more approachable license terms.