After a quick overview of the out-of-the-box posture conditions I do not specifically see Forcepoint product support so AFAIK there may be limited options. However, this does not mean you have no posture options available to you to force assessment against it. What is your end goal? To ensure it is installed and running? Or something more in depth, perhaps targeting a DLP version? Consider testing the following:
Service Condition: Ensure DLP is running
File Condition: Targeting executable via install dir path
Registry Condition: Any possible registry keys you could target that would meet your need
