M1 reports are based on Crystal Reports. You will need to buy at least one license from SAP Crystal Reports in order to edit reports in M1. https://www.sap.com/products/data-cloud … ml#buy-now
The best way to handle licensing in my opinion is to limit access to the Cyrstal Reports software by setting file/folder permissions so that only to users in a special LDAP/AD group can access the software. You need to buy licenses for the maximum number of people in the group. If your group has 5 users that can edit Crystal Reports, that means you need 5 licenses. I think it is more realistic to buy something like 2 licenses, meaning 1 main user and 1 ‘on demand’ user.