This is the first Morepath release of 2016 and the biggest Morepath release in a while. The major change in Morepath 0.13 is that it is now build on the Dectate meta-framework for configuration.
Morepath's configuration system is finally documented in the form of Dectate. Developers can extend Morepath with new configuration directives and new configuration registries and they behave exactly like the native ones. They're built the same way.
Dectate offers powerful features that I believe takes Morepath's decorator-based configuration system far beyond what you can do with most other web frameworks, which typically use a Python file for configuration, or use an ad-hoc decorator-based system. Too bad almost nobody seems to realize how much power this brings to the developer... A query tool for configuration, for instance.
The only framework with an equivalent system is Pyramid, but I think Morepath still has some features it does not: Morepath allows multiple independent configurations in the same run-time, for instance.
With the introduction of Dectate we've dropped Morepath's dependency on Venusian. Venusian was certainly valuable to Morepath, but over time we started to have some issues with it: its requirement to scan Python code was a barrier for beginners, and in some cases it could impact performance.
Dectate does not require scanning of packages in order to find registrations, but it can certainly be handy to be able to do so, as you can't miss any stray decorators in modules you didn't import anywhere else. Morepath now supports it through the new importscan dependency. importscan defines a recursive import function extracted from Venusian.