It's not based on whether a server is legacy or not, just on how congested it is.

The servers listed under the "Congested Worlds" headings on that list Rongway linked have a semi-permanent ban on new characters and incoming transfers. Until their numbers come down to a level SE is comfortable with, nobody will be starting on or transferring to Balmung, Gilgamesh, or a few of the overcrowded EU and JP servers.

Servers like Hyperion, listed under "Standard Worlds", may still have temporary new character creation bans, but those come and go according to how many people are logged in at the moment. Your friend may have better luck trying to create a character at off-hours, like early morning weekdays, when traffic tends to be low. Another option is create the character on another server and then use the World Transfer Service to move to Hyperion, (though that option costs money, so I'd try the early morning character creation unless he has an established character he wants to keep).


p.s. That website list only updates every few hours, but the temporary bans (identified just by "×" or "○" by the world names) can actually change more often than that, so in between those times that list may not be completely accurate in that regard. The only way to be sure is to try it and see if it works. The "New World / Preferred World / Standard World / Congested World" designations, on the other hand, stay in place until someone at SE decides to change the rules for them, so I think we can rely on that part to be kept up to date.