There are many useful resources for those who engage in developing extensions (aka. plugins / add-ons) to DataCleaner. To help you on your way, here's a list of useful links. If you think this list is missing a link, please let us know:
Tutorial: Developing a transformer
Tutorial: Developing an analyzer
Tutorial: Implementing a custom datastore
Javadoc: DataCleaner
Javadoc: MetaModel