Available with Workflow Manager license.
The 10.9.1 release of ArcGIS Workflow Manager (Classic) Server includes minor enhancements to the software and the documentation; no major new functionality is included with this release.
The stand-alone ArcGIS Workflow Manager (Classic) Server extension installer is no longer necessary at 10.9.1. However, the software must be authorized using your Workflow Manager Server extension license key on each machine on which it is installed.
Learn more about enabling ArcGIS Workflow Manager (Classic) Server in ArcGIS Server 10.9.1
For a complete list of enhancements and issues addressed, visit the product download page.