Is it required to add "jbpm-flow-builder" jars inside a Drools application classpath ?

Issue

• While packaging Drools libraries in a custom application the following Drools libraries (shipped with BRMS 5.3.1) were added initially to test the application however it does not work properly during testing.

drools-core-5.3.1.Final
drools-compiler-5.3.1.Final
drools-decisiontables-5.3.1.Final 
drools-templates-5.3.1.Final 
knowledge-api-5.3.1.Final

The application started working after adding the following dependency though.

jbpm-flow-builder-5.2.0.Final

• Is it really required to use jbpm-flow-builder jar to run a Drools based application?