Question: What was the loose sequel that came years after Return to Castle Wolfenstein was released?

Context articles: Castle Wolfenstein
Muse Software
Gaille Heidemann
Wolfenstein 3D
Beyond Castle Wolfenstein
4Kings
Return to Castle Wolfenstein
Firebug (video game)
Wolfenstein: Enemy Territory
Wolfenstein (2009 video game)

Castle Wolfenstein is a stealth-based action-adventure shooter video game developed by Muse Software for the Apple II.
 It was first released in 1981 and later ported to MS-DOS, the Atari 8-bit family, and the Commodore 64. "
Beyond Castle Wolfenstein" is its sequel.
Muse Software was a Baltimore-based software and computer game publisher and developer for the first generation of home computers.
 They first published for the Apple II under the name Micro Users Software Exchange, and later expanded to the Commodore 64, Atari, and IBM PC markets.
 They are best known for publishing the original "Castle Wolfenstein" in 1981 as well as its sequel "Beyond Castle Wolfenstein" in 1984.
Gaille Heidemann is an American voice actress, singer and songwriter known as the voice of Myriam the Mystic in Diablo III, Tempestra in Teenage Mutant Ninja Turtles, along with guest-starring roles in Legends of Dreanor and Legion for World of Warcraft, Kung Fu Panda - Legends of Awesomeness, James Bond, Jr, All Grown Up, Primetime Glick, The California Raisin Show, Return to Castle Wolfenstein among many others.
 As a teenager she became a studio session singer appearing on TV and movie soundtracks with the Jimmy Joyce Singers.
 She dubbed the singing voice for Patty Duke in Valley of the Dolls, and played the girl singer with co-stars Kim Milford and the rock band Moon in two ABC Wide World Mysteries produced by Don Kirshner.
 Her song Hollywood Movie Girls was recorded by Dusty Springfield and became the title and theme for the TV special Ann-Margret: Hollywood Movie Girls for which she also wrote special material.
 Gaille's rock n' roll impressions were featured on stage and film in Stars on 45 in Concert; Dream Street in Las Vegas, which won the Eppie Award for Best Show of the Year; and Forbidden Broadway in San Francisco.
 The Olsen Twins performed nine of her songs in their musical party series, You're Invited To Mary-Kate and Ashley's, including "Dancing Your Dreams", "Practice, Practice, Practice" and "Moonbounce Madness" all co-written with Adam Fields.
 She wrote, sang, produced and appears in "Obama Girl's Mama" the YouTube parody of the Obama Girl election videos directed by John Moffitt.
 Gaille has voiced over a hundred commercials for clients such as Coca Cola, Pizza Hut, and Goodyear Tires.
 She co-wrote and produced “Chuck & Di – the Tabloid Musical!”
 for an SRO run at the Long Beach Playhouse reviewed by Robert Koehler for the LA Times as "a swiftly paced crib of Gilbert and Sullivan, mixed with campy drag comedy out of Monty Python."
Wolfenstein 3D is a first-person shooter video game developed by id Software and published by Apogee Software and FormGen.
 Originally released on May 5, 1992 for MS-DOS, it was inspired by the 1981 Muse Software video game "Castle Wolfenstein".
 In "Wolfenstein 3D", the player assumes the role of Allied spy William "B.J." Blazkowicz during World War II as he escapes from the Nazi German prison Castle Wolfenstein and carries out a series of crucial missions against the Nazis.
 The player traverses through each of the game's levels to find an elevator to the next level or kill a final boss, fighting Nazi soldiers, dogs, and other enemies with knives, pistols, and other guns.
Beyond Castle Wolfenstein is a 1984 video game by Muse Software.
 It is the sequel to "Castle Wolfenstein", a prototypical stealth game.
 Unlike the original game, "Beyond Castle Wolfenstein" was originally developed simultaneously for both the Apple II and the Commodore 64, but was quickly ported to MS-DOS and the Atari 8-bit.
4Kings or Four Kings was a professional computer game esports clan/team based in the United Kingdom.
 The team had players competing in "Return to Castle Wolfenstein", "Quake III", "Warcraft III", "Unreal Tournament" and "Counter-Strike".
 The most famous member of 4Kings is probably "Warcraft III" player Grubby.
 Philip Wride was a manager of the team.
Return to Castle Wolfenstein is a first-person shooter video game published by Activision, released on November 19, 2001 for Microsoft Windows and subsequently for PlayStation 2, Xbox, Linux and Macintosh.
 The game serves as both a remake and a reboot to the "Wolfenstein series".
 This single player game was developed by Gray Matter Interactive and Nerve Software developed its multiplayer mode.
 id Software, the creators of "Wolfenstein 3D", oversaw the development and were credited as executive producers.
 The multiplayer side eventually became the most popular part of the game, and was influential in the genre.
 Splash Damage created some of the maps for the Game of the Year edition.
 A loose sequel, titled "Wolfenstein", was released on August 18, 2009.
Firebug is a 1982 computer game by Muse Software for the Apple II computer.
 The game was released on cassette tape and on floppy disk.
 It was written by Silas Warner, who created "Castle Wolfenstein" for the Apple II in 1981.
Wolfenstein: Enemy Territory is a free and open source multiplayer first-person shooter video game set during World War II.
 It was originally planned to be released as a commercial expansion pack to "Return to Castle Wolfenstein" and later as a standalone game.
 However, due to problems with the single-player aspect, the multiplayer portion was released on 29 May 2003 as a freeware standalone game.
 In January 2004, the source code for the game logic (not the game engine) was released to the benefit of its modding community.
Wolfenstein is a first-person shooter video game developed by Raven Software and published by Activision.
 It was released in August 2009 for the Microsoft Windows, PlayStation 3 and Xbox 360.