Categories are hardcoded and can not be changed. They represent ISO 9126 classification.
We plan to develop a tag mechanism in order to add any custom categories to rules. For example we could imagine a rule with tags "architecture" and "sonarj". Unfortunatly I can't give you any release date.
It's possible to add some rules to default profiles. Implement the method getProvidedProfiles() and return profiles named "Sonar way" or "Sun checks". Have a look at
FindbugsRulesRepository or
CheckstyleRulesRepository classes.