windows server licensing

i don’t understand windows licensing, after studing the microsoft site etc.

i bought a windows 2003 server with oem software with 5 users, my supplier tels me that users may log on local via rdp with the user licenses given with the windows software, but if you log on via www with rdp you need extra ts calls.

is this statement true ?

can yo log on with rdp to the server with 5 users simultaniously without ts service ?

or is there an other way to log on ?