Licensing is not yet enforced. In the near future it will be required to get sig-updates.
See excerpt from the readme:
*****
IPS SUBSCRIPTION SERVICE LICENSE
You must have a valid maintenance contract per sensor to receive and use
software upgrades, including signature updates from Cisco.com. Beginning with
IPS 5.0, an IPS Subscription Service License is required to install signature
updates.
You can request an IPS Subscription Service License for all sensors covered by a maintenance contract at this URL:
http://www.cisco.com/go/license
To manage your maintenance contracts use the Service Contract Center found at this URL:
http://www.cisco.com/cgi-bin/front.x/scccibdispatch?AppName=ContractAgent
With the initial release of 5.0, the first several signature updates will be
released without the license enforcement to allow you time to get your
maintenance contracts in order and your sensors licensed.
****
Hope this helps.
-Mario