Here follows a quick timeline of UO emulators, based on facts, fiction and wild guesses, numbered from first to last. I've included any dates I've been able to dig up, as well as the current (when I checked) homepages that exist for the various emus. Feel free to point out any flaws by contacting me at email@example.com.
(1)UOX -> (2)UOX2 -> (4)UOX3 -> | |->(10)UOXGold | |->(10)AUOX -> (11)AUOXCON | |->(13)Wolfpack | | | |-> (14)Sunshine/Sushix | | | |-> (16)NOX-Wizard | | | | |-> (24)Revelation | | | | | |-> (34)equinox | | | |-> (17)Lonewolf | | | | | |-> (20)UO-Inside Out | | | | |-> (21)Method | | | | |-> (38)Werewolf | | | |-> (18)Shard Emulator | |->(12)UOX-pi | |->(13)LoC | | |->(19)UOX Classic | | | |-> (28)UOX:NG | |->(27)UOX3 "Unofficial" | |->(41)uoOS (3)Fuse | |-> CFuse | |-> Thayland's Fuse | |-> FuseX (5)NWO/UOAWE/UOR/Unnamed (6)Grayworld -> TUS -> Sphereserver (7)UOOS |-> (Swords, never finished?) (8)POL (9)Trespasser -> Hellfire -> Hybrid (15)Epsilon (22)Atum (23)Tupi (25)RunUO | |->(35) RunUO-RE (later renamed RuOSI) | |->(36) SunUO (26)SteamEngine (29)MyUO (30)Psychotropic (31)AUOE (32)Athena (33)Canera-Project (37)Ultima Online: Shattered Legacy Server (39)UO:98 (40)JUOServer
1.) Jaegermeister (Denny Zuko?) creates the first version of UOX (Ultima Offline eXperiment)
2.) Cironian creates UOX2, rewriting UOX from scratch
3.) Fallo creates FUSE, a server expandable by user-made DLL-addons, such as CFuse, Thayland's DLL, and FuseX (by Craz).
4.) Cironian redoes UOX2, and the first public UOX3 version (0.37) is released Oct 22. 1997.
5.) A bunch of other UO servers that never really took off generally come to a halt when Cironian releases source for UOX3, including; New World Order, UOAWE - started Feb 9, 1998, by Gabriel, UOR, and An unnamed UO Server.
6.) Menace creates Grayworld early in 1998. It eventually evolves into TUS (The Ultimate Server), which again evolves into Sphereserver around April 2000).
7.) Sheppard creates UOOS - the first object oriented UO emu, or something.
8.) Syzygy(?) creates POL in the summer of 1998.
9.) What was later to become Hybrid was started sometime in 1998, around the time when the source for FUSE was released, and back then it went under the name Trespasser. Later it changed name to Hellfire, before being renamed as Hybrid.
10.) Armageddon makes his own version of UOX3, named AUOX, causing the first "branching" of any UO emu to occur :P
Some other people start working on another branch of UOX3, which they call "UOXGold".
11.) SpaceDog continues Armageddon's AUOX through "AUOXCon"(tinued)
12.) Lord Binary does his own version of UOX3, called UOX-pi - later to be merged into Wolfpack.
13.) Ripper's customized UOX3 code grows into Wolfpack, while Chaos's customizations become Legions of Chaos
14.) Sunshine, a derivate work of an early Wolfpack version, is started by M. Strobl sometime in 2000. In 2003, version 3 of Sunshine is reforked from Wolfpack, because of memory restraints/unreadable codebase in the original fork. The successor of Sunshine, Sushix, is never officially released.
15.) Epsilon is started by Kair in May 2001
16.) NOX-Wizard is created by xan using Wolfpack as base (25. June 2001)
17.) Wolfpack development splits in three (see below) as some WP devs pack up and start Lonewolf on November 9th, 2001.
18.) Shard Emulator, a Wolfpack v12.6 based emu, is started at the same time as Lonewolf.
20.) UO-Inside Out, a Lonewolf derivate started by Skyfire?, releases it's first version in early January.
21.) Method, a project derived from Lonewolf, is started by Melchir in early February 2002.
22.) Atum, a russian developed UO Emu, has it's first release in February 2002. It's closed source, and has no released packages.
23.) Version 0.1 of Tupi, a server written in Java, is released on the 4th of February 2002 by speka/dalzhim.
24.) Revelation, based on NOX-Wizard, enters the scene, on Aug 21st, 2002.
25.) Krrios reveals RunUO in early september 2002 - the first UO emu written in C#.
26.) Shadowlord starts working on SteamEngine, an open-source UO emu mimicing Sphereserver's functionality, on Sept. 29th, 2002.
27.) punt starts up UOX3 "Unofficial" on the first day of 2003, intending to rewrite the "JS"UOX3-version.
28.) UOX:NG - derivate work of UOX-Classic, started with big-endian 64 bit machines in mind, by Generic Player
29.) MyUO is created by Fabrizio Montesi, in October 2003.
30.) Psychotropic - A successor project to Hybrid, is started in December 2003 by Ian McNealy
31.) The initial revision of the source for AUOE (Advanced Ultima Online Emulator) is submitted to SourceForge on the 2nd of March, 2004, by f0xfire
32.) Athena - started March 10, 2004 by Kair
33.) Canera-Project - closed source project started 03-15-2004 by Sargo
34.) equinox - spin-off from NoxWizard makes it appearance on SourceForge on the 19th of September 2004
35.) Initial version of RunUO-RE (Russian Edition) is released to the public on New Year's Eve in 2004 by Wyatt, as a fork based off of 3rd party decompiled sources for the then closed-source RunUO, though it was later migrated over to the open-source version of RunUO. Eventually, from version 1.5.0 (with UO:SA support), it was renamed to RUOSI. Supports enhanced client and all expansions.
36.) Max Kellermann forks SunUO from RunUO on February 5th, 2005. It runs on Mono 1.1 (Linux, FreeBSD) out of the box.
37.) First release of Ultima Online: Shattered Legacy Server occurs on May 30th, 2005, by Maximilian Scherr (Max), though it had been under development on/off since summer 2002, and included a rewrite from scratch in 2003. It's intended for the Alpha version of the Ultima Online client.
38.) Zagyg starts Werewolf - based on Lonewolf - on December 7th, 2005.
39.) UO:98 is released on December 7th 2011, by Batlin. It is a port of the UO Demo server into a fully functional multiplayer UO server.
40.) JUOServer makes its appearance on SourceForge on January 22nd 201, as a Java-based Ultima Online server.
41.) uoOS (uo Old School?), puts up the first public version of its source-code, which is a branch off of UOX3 0.9x
Servers not placed in timeline as of yet(any info about these will be appreciated!):
?.) LCUOSE, based on UOX3, lives a short life and decays quickly.
?.) LOP makes a short entrance, but doesn't stay for long.
?.) UO Free
?.) RUOSI - a Russian-based fork from RunUO.
UOX3 - 22.Oct 1997 - by Cironian (Markus Rating)
Grayworld - Early 98 - by Menace
UOAWE - Monday Feb 9, 1998 - by Gabriel
POL - Summer 1998 - by Syzygy
Hybrid - 1998 - by McNealy, Sean Rose and Cycline3
UOX-pi - 8th Jan 2000 - by LB
Epsilon - May 2001 - by Kair
NoX-Wizard - 25.June 2001 - by xan
Revelation - August 21st 2001 - by ???
Lonewolf - 9th November 2001 - by LB & ???
Shard Emulator - 9th November 2001 - by frazurbluu
UOX-Classic - Nov. 17, 2001 - by Sargo
Method - February 10th 2002 - by Malchir
Atum - February 2002 - by Ramsess
Tupi - February 4th 2002 - by Guilherme Lanius (speka)/Gabriel Abut-Lussier(dalzhim)
RunUO - September 2002 - by Krrios
SteamEngine - 29. September 2002 - by Shadowlord
UOX3 "Unofficial" - 1st January 2003 - by punt
UOX:NG - September 2003 - by Generic Player
MyUO - October 2003 - by Luxor (Fabrizio Montesi)
Psychotropic - December 2003 - Ian McNealy
AUOE - March 2nd 2004 - f0xfire
Athena - March 10th 2004 - by Kair
Canera-Project - March 15th 2004 - by Sargo
equinox - September 19th 2004 - by prisonernumber7
RunUO-RE/RUOSI - December 31st 2004 - by Wyatt
SunUO - February 5th 2005 - by Max Kellermann
Ultima Online: Shattered Legacy Server - May 30th 2005 - by Maximilian Scherr (Max)
Werewolf - December 7th 2005 - by Zagyg
UO:98 - December 7th 2011 - by Batlin
JUOServer - January 22 2012 - by daneel_olivaw
uoOS - July 11th 2012 - by Xantier