April 2013 Update: Service shut down date confirmed as June 30, 2014.

As of September 1st, 2012, the Microsoft Lync Public IM Connectivity User Subscription License (“PIC USL”) is no longer available for purchase for new or renewing agreements.  Customers with active licenses will be able to continue to federate with Yahoo! Messenger until the service shut down date (exact date TBD, but no sooner than June 2013).

The PIC USL is a per-user per-month subscription license that is required for Lync Server or Office Communications Server to federate with Yahoo! Messenger.  Microsoft’s ability to provide this service has been contingent upon support from Yahoo!, the underlying agreement for which is winding down.

More than ever, Lync is a powerful tool for connecting across organizations and with individuals around the world.  Federation with Windows Live Messenger requires no additional user/device licenses beyond the Lync Standard CAL.  Next year, Skype federation will be added to this list, enabling Lync users to reach hundreds of millions of people with IM and voice.