Almost every SaaS product is multi-tenant: Salesforce runs one codebase that serves thousands of companies, each logically walled off from the others inside the same infrastructure. It's what makes SaaS pricing affordable -- the cost of running the software is shared across every customer on it.
The tradeoff is less customization freedom than a dedicated, single-tenant deployment would allow, which is part of why configuration and workflow design matter so much when implementing a multi-tenant tool.