The dataflow that loads data from Silverpop into Gigya involves renaming Silverpop fields to match Gigya's format, and using a JEXL expression in the field.evaluate step to transform the Silverpop "T/F" values to Gigya's "true/false". In this example, the subscription status is written to the data.subscribed field. If you are using Enterprise Preference Manager's communication preferences, you can write the status to any subscription field (e.g. subscriptions.mySub.email.isSubscribed). The various dataflow steps are described in greater detail here: Component Repository.