This reorganization of code is reflected in the hierarchy of projects that produce it: IPython is now an official subproject of the Jupyter project. IPython is Kernel Zero, in some sense the reference kernel, but in the end just one kernel among many. There are still some sections of code that are shared between the projects and need to be separated, but this is a relatively simple technical issue.

Even after the codebases became completely separate, Jupyter will constrain the future of IPython due to requirements for continued compatibility. Although IPython can be used as an independent tool (as this book attempts to demonstrate), its role in the Jupyter project greatly increases its user base.

At first glance, this would seem impossible. The Jupyter project is large and contains more subprojects than could be comfortably listed here (see http://jupyter.readthedocs.org/en/latest/subprojects.html for a complete list), making any attempt at staying compatible a nightmare...