Yes they are the same, but with a lot more added functionality.
these being things like
remote apps
remote TS Gateway
Easy print (resolves lots of driver errors)
and lots lots more
Trust me, 2008 is far better than 2003 TS, though you will need new CALS as you mention..
http://www.microsoft.com/windowsserver2008/en/us/rds-product-home.aspx