It does need documenting but the basics are something like:
Configuration config = ...
Session session = new Session(config);
CommandBuilder builder = new CommandBuilder(session, sql, args);
somePanel.add(builder);
builder.addValueChangeHandler(new ValueChangeHandler() { @Override public void onValueChange(ValueChangeEvent event) { .. } })
The JS adapter shows a complete example: https://github.com/salk31/RedQueryBuilder/blob/master/redquerybuilder-js/src/main/java/com/redspr/redquerybuilder/js/client/RedQueryBuilder.java