I didn't know there was a "server" edition as such.
Anyway, you need to pick a mirror from the list, then choose either http, ftp or rsync type download. Then you need to choose either 32 bit (i386, i686) or 64 bit (x86_64) edition.
Then download the dvd or live cd or whatever you want. Read the README.txt file before you start.
Here's an http
mirror for 6.3 in South Africa.
Or choose from the
full list.