Installation of KIE Workbench is not mandatory. You can use jBPM in embedded as well, but then you have to take care of persistence and transaction. You have to develop your own service to handle process instance from remote machine. If you use KIE Workbench server will take care of persistance, transaction, you can use REST API's exposed by server. Its upto your requirement which one to use. Hope it helps.. thanks..
The workbench is not required, but it does offer quite a few (additional) features that might (or might not) be useful for you. For example:
- it's 100% web-based, so doesn't require installation
- comes out-of-the-box with an execution server and remote APIs, so you can send commands to it (rather than embed the engine in your application)
- it comes with tooling targeted to less technical users (as well - developers can use it too), like data and form modelers, task lists, dashboards, etc.
If you're unsure if it might be useful, I would recommend just using the jbpm-installer and taking a look at the features it provides by following the 10min demo. If it's not what you need, you can use simply embed jBPM in your application as well.