component architecture. The libraries underlying BlueBream have been evolving into a collection of useful libraries for web application development rather than a single, monolithic application server. BlueBream includes separate packages for interfaces, component architecture, HTTP server, publisher, Zope Object Database (ZODB), Zope Page Templates, I18N, security policy, and so on. The component architecture is used to glue these together. The component architecture is configured using a ZCML (Zope Configuration Markup Language), an XML based configuration file language. The Zope 3 project pioneered the practice of sprints for open source software development. 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. During the sprints various practices drawn from agile software development are used, such as pair programming and test-driven development. Besides the goal of developing software, sprints are also useful for geographically separated developers to meet in person and attracting new people to the project. They also serve as a way for the participants to learn from each other. BlueBream is considered a stable framework, used on production projects worldwide, most notably Launchpad. Zope Toolkit As a result of the development of Zope 3 / BlueBream, there are now many independent Python packages used and developed as a part of BlueBream, and although many of these are usable outside of BlueBream, many are not. The Zope Toolkit (ZTK) project was started to clarify which packages were usable outside BlueBream, and to improve the re-usability of the packages. Thus the Zope Toolkit is a base for the Zope frameworks. Zope 2.12 is the first release of a web framework that builds on Zope Toolkit, and Grok and BlueBream were set to have releases based on the ZTK during 2010. Grok In 2006 the Grok project was started by a number of Zope 3 developers who wanted to make Zope 3 technology more agile in use and more accessible to newcomers. Grok has since then seen regular releases and its core technology (Martian, grokcore.component) is also finding uptake in other Zope 3 and Zope 2 based projects. Zope 4 In late 2017, development began on Zope 4. Zope 4 is a successor to Zope 2.13, making many changes that are not backwards compatible with Zope 2. Zope 5 Zope 5 was released in 2020. Zope Page Templates As mentioned previously, Zope Page Templates are themselves