RunUO is an UO Server yes - but it still falls under the category "UO server emulator" when using the same definition of the word that has been used to describe this and similar software since 1997. It is no less an UO server emulator than UOX3/Sphere/POL/WolfPack/Lonewolf is or Fuse/UOOS/NWO/UOAWE/Grayworld was, and neither of those are/were any less an "UO server" (by definition, not feature-wise) than RunUO is..
Definitions of words and terms change according to their usage; take the words "gay" and "fairy" as examples. The meaning of those words changed in the 20th century, because over time, people used them to describe people with affections for members of the same sex.
Even if it might be "technically wrong" to call RunUO and similar programs "UO server emulators", historical usage of the term (Nearly 9 years now) has set a strong precendence.
I leave you with some examples of said historical usage of the term:
From the readme.txt of UOX3 0.50, released 24 December 1997:
Welcome to UOX3, the first multiplayer-capable
server emulator for Ultima Online. (No longer the only one
From the frontpage of
http://uox.warlords.com as of May 17, 1998:
UOX is an Ultima Online Server Emulator.
Use this program to play UO offline
Raph Koster's "Online World Timeline", about 1998:
In September, UOX, the first UO server emulator, manages two simultaneous connections with UOX3.
felisandria posting on gamedev.net forums in August 1999:
The UooS emulator (Ultima Object-Oriented Server) pretends to be one of the servers that Origin Systems provides at a fee of $10/month to play Ultima Online. Basically you run the emulator on your computer, tell all your friends who want to play with you your ip address and provide them with passwords, then log your Ultima Online client into the server. Because the emulator is a server, it contains none of the information taken care of by the client (most notably the graphics and GUIs of the game) so unless you have Ultima Online, you will not be able to use the server. Technically the use of emulators became a violation of the user's agreement of Ultima Online when T2A came out, however, the legality of that change in the contract is under question.
From the FAQ-page of cfuse.com, April 2000:
Q: What is Fuse?
A: Fuse is an Ultima Online server emulator engine, it by itself does not run, you must have a dll to use it, dlls are also where all the features come from. Of course, if you are here, you know about Cfuse.
Sphereserver.com, june 14 2000:
Another update to the preview version of the SPHERE game client has been posted.This version includes starting skills and stats choices, and limited skill functionality.If you decide to try the SPHERE client, please report your bugs in the SPHERE Client forum in the Discussion area.Our preview release of this client is an effort to revitalize the EMU community, the SPHERE development team has decided to offer a preview of their soon to be released client. This client may be used with ALL emulators in the future and is in an alpha state. Please feel free to download the preview version in our Development / Files area.
Runuo.com's frontpage as of october 2002 used the word "emulator" to describe similar software several times:
Reliable, stable and easy to use... 3 words that do not describe any UO server (or emulator) out there. We are changing that rapidly!
...
By designing Run UO from the users perspective we have given ourselves an advantage over most if not all UO Servers and emulators out there.
...
We started behind the eight ball, yet progressed more in a few months than some servers or emulators have in years.
...
The combined experience on this team enables us to miss the problems that typically plague 'startup servers or emulators'.
From #runuo on July 27th 2004:
Session Start: Tue Jul 27 05:14:48 2004
Session Ident: #runuo
*** Now talking in #runuo
*** Topic is '#RunUO : The only choice for UO server emulation || http://www.runuo.com/'
*** Set by Zippy- on Sun Jul 25 22:49:24
...
<mrwiggles> but runuo is the only emu that'll support over 10 people online at teh same time :\
From #runuo on February 5th, 2006:
[23:15] * Zippy- changes topic to 'RunUO - Best UO emulator, ever. || So Steelers. Seattle blows.'
From the description written at the top of POL's forums as of July 11, 2006:
An Ultima Online Server Emulator