PlanMill Multi-company and multi-currency is an add-on feature.
Multi-company means there are several "My company" type of Accounts in the same PlanMill.
All my companies are able to e.g. invoice through the same PlanMill.
Multi-currency means you can use more than 1 currency for sales.
One currency is default currency. All reports and list views use this base currency to convert to user currency.