Darren,
There is a base PCM (ProCurve Manager) product that is free, which provides some very basic management capabilities. To enable more advanced management features, referred to as PCM+, you need a license whose cost is based on the number of devices you have. The other "plug-in" applications for PCM (IDM - Identity Driven Manager, NIM - Network Immunity Manager, PMM - ProCurve Mobility Manager) are all for-fee applications whose cost is also graduated on some criteria having to do with the size of your network.
All of the applications can be tried for 60 days at no cost. Perhaps you're within that 60-day window right now ...?
Regards,
SVB