Excelente artigo!!
The Ultimate Guide to Windows 2003 Terminal Server Licensing
http://www.brianmadden.com/blogs/brianmadden/archive/2004/04/01/the-ultimate-guide-to-windows-2003-terminal-server-licensing.aspx
Este artigo também complementa informações:
KB 823313
Windows Server 2003 Terminal Server licensing issues and requirements for deployment
http://support.microsoft.com/default.aspx?scid=kb;en-us;823313