Hi BOFHEN,
Customers with Lync Server 2010 with active Software Assurance (SA) qualify for federation with Windows Live Messenger and AOL without additional licensing
requirements.
However, customers that do not meet the qualifying requirements should buy the Lync Public IM Connectivity (PIC) license for federation with Windows Live Messenger
and AOL.
For details, see the
Public IM Connectivity Provisioning Guide. Hope helps.
Noya Lau
TechNet Community Support
