This post talk about the Windows Server 2008 RDS CAL which replaces the older Terminal Services (TS) CAL. If you already own 2008 TS CALs; you can use Windows Server 2008 TS CALs with Windows Server 2008 R2 Remote Desktop Services. If you’ve Windows Server 2003 TS CALs you’ll need to buy new RDS 2008 CALs. Microsoft’ll be offering Windows Server 2008 RDS CALs at a transition price equivalent to old TS CAL from Sep 1, 2009 until Dec 31, 2009. Beginning Jan 1, 2010 any new RDS CAL sales’ll be at normal RDS CAL price. The Windows Server 2008 TS CAL’ll no longer be available after Sep 1, 2009 if you’ve any version of Terminal Services or Remote Desktop Services you should purchase Windows Server 2008 RDS CALs. Application compatibility and management are significant drivers of cost for many TS / RDS customers. By including the right to use App-V for TS as part of the TS & RDS CALs we have simplified licensing. The App-V CAL for TS will not be available for purchase after November 1st 2009.
More info: RDS blog