Running a public server means (presuming the MOUL architecture isn't too different from UU or Alcugs) running one or more auth servers which will allow players to login, one or more lobby servers that manage connections, messages, linking, etc, and one or more data servers that actually serve you the Ages you're linking into.
Chogon has already laid that to rest, I guess, by stating elsewhere that the MOUL architecture is very different to UU. What that really
means at the end of the day is still open to speculation, but the general principle stated above seems to be right.
What we do know is that MOUL, at launch, had 21 game servers, plus the auth and data servers (by name anyway; some of the IP addresses were shared, and there's no particular evidence I have to say that those IPs were each on a physically distinct host). I can't find my notes on this right now, but in the latter months, the number of (active) game servers was roughly halved. I think that happened round about the time the cones were removed.
However, I hope that it'll still be possible to create a small, "domestic" configuration that would allow the creative types to do initial testing of their own Fan Content.
We don't yet know how Cyan will put together their Open Source Licence - it doesn't have to exactly follow one of the existing models. I've got a little thought in the back of my mind that Cyan might elect to retain the Auth server (as in UU), so they could track the level of usage. Sorry, I'm drifting into speculation again.