Zope is a family of free and open-source web application servers written in Python, and their associated online community.

[4][5] Over the last few years, the Zope community has spawned several additional web frameworks with disparate aims and principles, but sharing philosophy, people, and source code.

BlueBream (earlier called Zope 3) is less widespread but underlies several large sites, including Launchpad.

[6] What is now known as Zope 2 began with the merging of three separate software products – Bobo, Document Template, and BoboPOS – into the Principia application server.

At the behest of its largest investor, Opticality Ventures, Principia was re-released as free software under the name Zope in 1998.

Zope 3 is a complete rewrite that preserves only the original ZODB object database.

The existence of two incompatible Web frameworks called Zope has caused a lot of confusion.

ZPT offers a very limited set of tools for conditional inclusion and repetition of XML elements.

One significant advantage of ZPT templates is that they can be edited in most graphical HTML editors.

[11][12] BlueBream is distributed under the terms of the Zope Public License[13] and is thus free software.

Zope 2 has proven itself as a useful framework for Web applications development, but its use revealed some shortcomings.

The goal was to create a more developer-friendly and flexible platform for programming web applications than Zope 2 is.

The project began with the development of a component architecture, which allows the structuring of code into small, composable units with introspectable interfaces.

In Zope 2 there had been many behavior requirements to allow objects to participate in the framework, which resulted in a large amount of mixin base classes and special attributes.

The Zope 3 project pioneered the practice of sprints for open source software development.

[15] Sprints are intensive development sessions when programmers, often from different countries, gather in one room and work together for a couple of days or even several weeks.

BlueBream is considered a stable framework, used on production projects worldwide, most notably Launchpad.

As mentioned previously, Zope page templates are themselves XHTML documents, which means they can be viewed and edited using normal HTML editors or XHTML compliant tools (a big advantage compared to other template languages used for Web applications).