It's part of Enterprise Edition.
The following conditions must be met before you can use the broker:
The primary and standby databases must be using the same version of Oracle
Database 11g and each can be installed in either a single-instance or multi-instance
environment. The database must be licensed for Oracle Enterprise Edition or
Oracle Data Guard Broker 11g Release 2 (11.2) E17023-06
Section 2.2 Prerequisites