WS2003 net time service and accessing it

A couple of questions:

Does the Windows Net Time service available on WS2003 run as a basic NTP server, i.e use port 25 and abide by the ntp protocol?

If so, how can I get a PC or other network device NOT on the AD domain to update it's clock from the WS2003 time server?

If I try it on a workstation not on the domain, I get a "System error 5 has occured. Access is denied". Is this configurable in a GPO or something?

What I really want to be able to do is sync some other devices which aren't remotely W32 platforms (bespoke servers but which can have their internal clocks synced with a NTP server).

Of course, I guess if the windows time service is a MS-specific protocol that isn't NTP-compatible, I'm not going to get anywhere. :(

Thanks