In Project Explorer view, right-click project and click OpenShift > Configure Markers. Click Enable JPDA check box. The text description of this marker states '.. the JBoss AS 7 application server' twice.

But when I created my app I selected the JBoss EAP 6 cartridge so this text seems wrong.

To resolve either:
a) make two versions of the text one for JBoss AS cartridge and one for JBoss EAP cartridge
b) make description neutral, e.g. just 'the application server'

^ neutral is probably best as could also presumably select Tomcat cartridge for app and would also be able to set enable jpda marker.