Replication Server 15.7 is released as the Enterprise Edition.
Replication Server 15.7 includes enhancements to real-time loading (RTL) replication to Sybase® IQ. If you are using the Replication Server Real-time Loading Edition, you can use the RTL enhancements by upgrading to Replication Server 15.7.
See Replication Server Installation Guide > Planning Your Installation > Obtaining a License.