Replication Server 15.0.1 does not require the REP_SSL license, as SSL now comes as a part of the basic REP_SERVER license.
You can enable SSL using rs_init; you can enable or disable SSL using configure replication server with the use_ssl option.
To use configure replication server, enter:
configure replication server set use_ssl to 'on'
Set use_ssl to off to disable SSL. By default, SSL is not enabled on Replication Server. When use_ssl is off, Replication Server does not accept SSL connections.
use_ssl is a static option. You must restart Replication Server after you change its value.