Article Cover by Lia Avant

miniGuide - to the Zope Public License (ZPL)

On December 3, 1998, Linux Weekly News reported that Digital Creations, as Zope Corporation was known at the time, was releasing their application server as open source. In a article, Liz Coolbaugh, LWN editor, said: "From here on out, Zope will rise or fall based on how well its open source compatible license is received in the community and how well it works for the people who give it a try."

This miniGuide explains the Zope Public License to decision makers. We focus on the history of the license, its motivations, and how it applies in practice.

Digital Creations / Zope Corporation took its roots and open source identity from the Python community. Python was for many years governed by an exceedingly minimal license. This was intentional. Python's creator, Guido van Rossum, and others in the Python community, wanted to promote wide usage, including use by businesses. In addition, since there was little worry about "getting ripped off" Python chose a different direction than the GPL and the copyleft movement.

Over time, though, Python's license and intellectual property status became a challenge. Guido moved from CWI to CNRI, and then to BeOpen. Each employer left its mark on the lineage of Python's license. Also, one of the employers raised the issue of intellectual property: who owns the code, and could an indemnified version of Python be produced?

The first open source release of Zope came with a 1.0 version of the Zope Public License. As explained on the License Page, the ZPL 1.0 was based almost directly on the Apache Public License. Digital Creations (DC) viewed Apache as a singular success in its approach to community and business, a success they wanted to replicate. In fact, this early decision has left an indelible mark on the nature of the Zope world: it has always been more business-oriented than other open source projects.

The ZPL 1.0, though, deviated from the Apache license in one way. While DC kept the advertising clause that appeared in the Apache license, DC also added a request (though not a requirement) of Website attribution. This meant that all Websites that used Zope could be identified as Zope Powered.

The ZPL 1.0 quickly gained Open Source Initiative certification as "Open Source", though it was also listed as GPL-incompatible, based on the advertising clause.

During initial discussion in the nascent Zope community, Digital Creations expressed clearly the philosophy that Zope should take a business-friendly approach to license, copyright, and intellectual property. This approach generated displeasure amongst copyleft (GPL) advocates. However the counterarguments from pro-business members in Zope were reasoned and strong.

Regarding intellectual property, Zope had an easier course than Python. All the code for Zope was produced by Digital Creations. Furthermore, only Digital Creations could make changes to the source code. Until 2001, Zope was, in fact, open source in license only.

Thus, the basic course was set, although significant changes occurred along the way.

In 2000 and 2001, Nicolas Pettieaux, who worked with the government in Belgium, raised the question of GPL compliance. He articulately explained the state of open source in Europe, particularly in public administrations, and indicated that Zope was losing competitiveness because it couldn't be combined with GPL in larger projects.

From that discussion, Zope Corporation undertook a serious review of the ZPL's goals, as well as the changing nature of open source. Would it be possible to maintain the business-friendly nature of Zope while attaining GPL compatibility from the Free Software Foundation?

In November 2001, Zope Corporation announced a draft of the ZPL 2.0 which had received approval from the Free Software Foundation as GPL-compatible. This new version featured one major change: the advertising clause was dropped. (Note: the attribution request had already been dropped in version 1.1.)

Parallel to the license change, Zope Corporation was also moving to a model of community development. The Zope source code repository could now be modified by developers not employed by Zope Corporation. This produced a Contributor Agreement that helped preserve some of the intellectual property goals of Zope, as contributor FAQ. This contributor agreement was based directly on the Mozilla contributor agreement, with a clever addition of a "joint ownership" model to solve problems faced by Mozilla.

As a license, the ZPL is very standard in relation to the BSD-derived licenses such as the Apache license, with the exception of the advertising clause.

Specifically, the license specifies the terms of use as nearly unlimited. The copyright notice must be maintained and the name of Zope Corporation cannot be used as part of the software usage. Within the ZPL there is a stipulation about trademarks, indicating that the terms are covered elsewhere. (This is discussed below.) Finally, there the ZPL contains a standard disclaimer about no warranty.

In short, Zope can be used in nearly any way the user pleases. This fact has repeatedly provoked the "Aren't you afraid of being ripped off?" response over the years. The spirit has been, "No". Zope's attitude is more one of growing its market share in any direction possible.

Since Zope is a tool more than a product, it suffers less from the threat of being ripped off. Zope is a platform atop which individuals and companies add value in order to solve a problem. Thus, the value of Zope itself, as an intact redistribution, was thought to be lower than that of a ready-to-use product.

In most ways this theory has proven valid. There are no known cases of Zope, and Zope alone, being resold for enormous sums. Instead, the generous distribution conditions have helped generate a large market of Zope solution providers.

The legal status of Zope is in very good condition, relative to most open source projects. The Zope Public License is well attuned to the nature of the Zope community, which itself has a business-friendly nature. Perhaps the only improvement to contemplate is to rid the world of yet-another-license by adopting something standard, such as the Apache License.

Thanks to the contributor agreement, all software in Zope is from a known origin, with an actual signature on file, and covered under the ZPL. Moreover, the joint ownership model means that Zope can be managed centrally without being completely "owned" by a single entity. Thus, the question of "What if Zope Corporation was bought by Evil, Inc.?" is less of a concern for the contributions of non-Zope Corporation employees.

Regarding potential future issues, there are two that come to mind. First, since much of the code in Zope was originally written by Zope Corporation, what is the joint ownership status for that code? It appears that both partners of that code are, in fact, Zope Corporation. The contributor agreement requires that all code be perpetually available under an open source license, but it isn't clear if Zope Corporation is legally a "contributor".

Second, and more problematic, is the trademark question. The license says that the trademarks are governed by a separate document at Zope Corporation's Website. Returning to the "What if ZC were bough by Evil, Inc.?" scenario, while the code would be free, the name "Zope" could be disallowed from use or used for un-competitive purposes. Hopefully , it will be possible to close this loophole in the future.

The Contributor Agreement (PDF):
http://dev.zope.org/CVS/Contributor.pdf

Zope 3 Contributor FAQ:
http://hathaway.freezope.org/Software/Ape

Paul Everitt: was co-founder of Zope Corporation, serving in a number of positions, including Vice President of Products, CEO, and Chief Strategy Officer. Before co-founding Zope Corporation, Paul was an officer in the United States Navy. He received a degree in materials engineering from the University of Florida in 1990. In 2002, Paul moved with his family to Rennes, France to start Zope Europe.