Good news from FCS Blog.
“Customers who license the Client Security agent on a per-user basis can provide the Client Security agent to employees at no additional cost for protecting home computers. These home-based Client Security agents must be deployed in an unmanaged configuration; they will not be able to report to your Client Security servers in your enterprise.
The network administrator must distribute the required files to home users. For more information on Client Security licensing, see How to Buy Forefront Client Security (http://go.microsoft.com/fwlink/?LinkId=93608). For more information on using Client Security to protect home computers, see Protecting home computers (http://go.microsoft.com/fwlink/?LinkId=104969) in the Client Security Deployment guide.”
Source: FCS Team Blog