The readme states, "listen to code event widget_framework_ready." Here is the full section:
Also, anyone who wants to develop widget to use with the framework can do it in just a few steps. The framework will take care of everything and developers only need to focus on getting the business done. There are 2 things to do: listen to code event "widget_framework_ready", push your class name in to the array to register your widget renderer. After doing so, you can start coding your renderer by extending the base class "WidgetFramework_WidgetRenderer"
PHP:
class MyWidget_WidgetA extends WidgetFramework_WidgetRenderer {
}