Resell CommerceShip under your own brand
Put your domain and logo on every portal, email, and document, and give each client a separate tenant with the data separated in the database. Each client logs in to a portal on your domain, with your branding.
How a client sees CommerceShip under your brand
Brand the app and every surface, provision an account for each client, and let each client sign in and see only their own data.