Microsoft has released the following KB article:
Hotfix updates the Software Requirements UI for Mac software distribution operating systems in System Center 2012 Configuration Manager SP1
Summary:
This hotfix adds Mac OS X 10.9 to the Software Requirements user interface (UI) for Mac software distribution operating systems in Microsoft System Center 2012 Configuration Manager Service Pack 1 (SP1).
Full details at:
http://support.microsoft.com/kb/2918997