Note that InfoSphere Change Data Capture is a heterogeneous replication and data integration solution which replicates to/from log based change data capture platforms: DB2 (LUW, z, i), Oracle, SQL, Sybase, Informix and SolidDB. It can also target DataStage, JMS Queues and Teradata. Whereas InfoSphere Change Data Capture for Oracle Replication is a different product, and is designed for Oracle-Oracle High Availability.
CDC and Replication Server are different products, but have some overlapping function. With Replication Server's new Q Capture for Oracle databases, IBM's helping Replication Server customers get Oracle data into DB2. InfoSphere Change Data Capture for Oracle Replication is for Oracle-Oracle replication. So, the similarity is only that they can both get changed data from Oracle. Other than that, the implementations and target audiences are different.