Product

SBS 2011 CAL Suite: For each user or device accessing the SBS 2011 Standard network
SBS 2011 Premium Add-on CAL Suite: For only those users or devices accessing the SBS 2011 Premium Add-On SQL component functionality.
For SBS Premium, in addition to needing a SBS 2011 CAL Suite, you need a Small Business Server 2011 Premium Add-on CAL Suite for each user or device that accesses your instances of SQL Server 2008 R2 Standard Edition for Small Business. For access to your instances of Windows Server 2008 R2 Standard technologies, you may use a Small Business Server 2011 CAL Suite or SBS 2011 Premium Add-on CAL Suite.