When the 2003 server is first installed it assumes it will take you a while to get the license server set up, so from the time the first user logs in via terminal services it gives you 120 days to get the licence server in place.

To log on to this remote computer, you must have Terminal Server User Access Permissions on this computer. By default, members of the Remote Desktop group have these permissions. If you are not a member of the Remote Desktop Users group or another group that has these permissions, or if the Remote Desktop User group does not have these permissions, you must be granted these permissions manually.

After 120 days it requires that the users logging in are in the "Remote Desktop User Group" or that they have the "Terminal Server User Access Right". There are also licence requirements