A restricted use of Oracle Access Manager(OAM) & Oracle Internet Directory(OID) is allowed with WebCenter Suite Plus licensing which is one of the most common licenses available to Customers implementing a WebCenter Portal.
Thus OAM & OID can be used to provide Single Sign On (SSO) between WebCenter , UCM/Content & IPM without the client having to buy any additional licenses albeit with a few technical limitations.
In addition out of the box features like Impersonation can be leveraged easily.
On a whole this should help customers easily leverage Single-Sign-On using OAM & use Oracle's LDAP - OID when implementing a WebCenter Portal.
"Oracle Access Manager(OAM) for enabling Single-Sign On (SSO) between WebCenter Portal components. Use of Oracle Access Manager to a) enable SSO for any custom services or functions or third party applications;
b) Direct Oracle Access Manager SDK calls; or c) Third party directory integration, is not allowed.
Oracle Internet Directory(OID) - The use of OID is restricted to storing credentials and policies specific to WebCenter Portal and its delivered components."
1) OAM & OID alongwith the WebTier would need to be installed in the same VMs as Webcenter Portal when leveraged as a part of this licensing.
This makes it slightly different from Oracle's recommended deployment Architecture for OAM.