From the PressPass announcement: 

Microsoft is changing its public instant messaging connectivity (PIC) license requirements for Office Communications Server connectivity to the Windows Live and AOL public IM networks. Now, customers with Office Communications Server 2007 R2 Standard CAL (or equivalent Software Assurance rights) will no longer require an additional license to connect with the millions of people who use Windows Live and AOL for instant messaging and presence. This change took place in July for Windows Live, and is scheduled for AOL in October 2009.

You can read the rest of the PressPass announcement here: http://www.microsoft.com/presspass/features/2009/oct09/10-01ucinterop.mspx