Hi,
If your organization has a Microsoft 365 Apps for enterprise subscription, you can use Office Online Server internally, but making it available to customers as part of a SaaS application may require additional licensing.
Your SaaS customers need the appropriate license to use the features of Office Online Server. This means that while your organization can use an existing Microsoft 365 subscription to deploy and run Office Online Server, your customers will still need their own licenses to legally use these features.We recommend that you confirm that your Microsoft 365 or Office 365 subscription includes Office Online Server plans.
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