Hi @Mike ,
Thanks for reaching out and apologies for the delay in response.
- Does this license carry over when they authenticate to access an app hosted in B2C?
Azure AD B2C is separate from Azure AD for enterprises and uses its own licensing model. Licenses assigned in your main Azure AD tenant (P1 or P2) do not carry over to B2C. Users in your B2C directory need their own licenses for features like Self-Service Password Reset (SSPR), Multi-Factor Authentication (MFA), or Conditional Access in B2C.

- Are they going to be counted against MAU billing regardless of their license in our main Tenant?
Azure Active Directory B2C (Azure AD B2C) pricing is based on monthly active users (MAU), which is the count of unique users with authentication activity within a calendar month. Every unique user who authenticates with your B2C applications in a given month is counted as an MAU. This billing is independent of their license in your main tenant. Even if they have a P1 or P2 license in your main tenant, they will still be counted as an MAU when using B2C services, and you'll be billed accordingly.
Reference - https://learn.microsoft.com/en-us/azure/active-directory-b2c/billing#mau-overview
- if a user is counted as MAU, can it access non-microsoft applications hosted in B2C? Example: oracle fusion.
Azure AD B2C can be used to authenticate users for both Microsoft and non-Microsoft applications. This includes applications like Oracle Fusion, if you configure them properly to use Azure AD B2C as the identity provider. Users will go through the B2C authentication process regardless of the application they're accessing. The MAU count applies to all authentications, including access to non-Microsoft applications hosted in B2C.
Hope this will help.
Thanks,
Shweta
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