Question: When was the Half-Life first-person shooter game released by game development community MapCore? 

Context articles: Half-Life 2: Deathmatch
Half-Life: Blue Shift
Half-Life 2: Episode One
Half-Life (video game)
Minh Le
List of Valve Corporation video games
Half-Life: Decay
MapCore
Half-Life: Opposing Force
Vivisector: Beast Within

Half-Life 2: Deathmatch is a multiplayer first-person shooter video game developed by Valve Corporation.
 Released on Steam on November 30, 2004, it uses many of the assets from "Half-Life 2" and its Source engine.
 It features new levels, optimized for multiplayer arena play, and a few new weapons.
 Also included are portions of the game's source code, which were the basis for many early Source-based multiplayer modifications.
 The game is the successor to the popular multiplayer component of the original "Half-Life", but is offered as a separate product from "Half-Life 2".
 "Deathmatch", like "Half-Life"' s multiplayer, does not develop any part of the plot or story of the "Half-Life" series.
Half-Life: Blue Shift is an expansion pack for Valve Software's science fiction first-person shooter video game "Half-Life".
 The game was developed by Gearbox Software with Valve Corporation and published by Sierra Entertainment on June 12, 2001.
 "Blue Shift" is the second expansion for "Half-Life", originally intended as part of a Dreamcast version of the original game.
 Although the Dreamcast port was later cancelled, the PC version continued development and was released as a standalone product.
 The game was released on Steam on August 24, 2005.
Half-Life 2: Episode One is a first-person shooter video game, the first in a series of episodes that serve as the sequel to the 2004 "Half-Life 2".
 It was developed by Valve Corporation and released on June 1, 2006.
 Originally called "Half-Life 2: Aftermath", the game was later renamed to "Episode One" after Valve became confident in using an episodic structure for the game.
 Similar to "Half-Life 2", "Episode One" also uses the Source game engine.
 The game debuted new lighting and animation technologies, as well as AI sidekick enhancements.
Half-Life (stylized as HλLF-LIFE) is a science fiction first-person shooter video game developed by Valve, released in 1998 by Sierra Studios for Microsoft Windows.
 It was Valve's debut product and the first in the "Half-Life" series.
 Players assume the role of Dr. Gordon Freeman, who must fight his way out of a secret research facility after a teleportation experiment goes disastrously wrong, fighting enemies and solving puzzles.
Minh Le (Vietnamese: Lê Minh, born June 27, 1977), also known by his online nickname Gooseman, is a Canadian video game programmer who co-created the popular "Half-Life" mod "Counter-Strike" with Jess Cliffe in 1999.
 He was later employed by Valve Corporation, the developers of "Half-Life", and worked for 8 years in Korea on the multiplayer first-person shooter "Tactical Intervention".
 He is currently a contractor on the multiplayer survival first-person shooter "Rust".
 In the small-team games that he has worked on, Le has been a programmer, modeler, and designer.
Valve Corporation is an American video game developer and publisher founded in 1996 by Gabe Newell and Mike Harrington.
 The company is currently based in Bellevue, Washington.
 Valve's first game was "Half-Life", a first-person shooter released in 1998.
 It received universal acclaim and sold over 9 million units in retail.
 Alongside "Half-Life"' s launch, Valve released development tools to enable the player community to create content and mods.
 The company then proceeded to hire the creators of popular mods, such as "Counter-Strike", which became the most popular multiplayer first-person shooter for the next decade.
Half-Life: Decay is a multiplayer-only expansion pack for Valve Software's first-person shooter "Half-Life".
 Developed by Gearbox Software and published by Sierra Entertainment, "Decay" was released as part of the PlayStation 2 version of "Half-Life" in 2001.
 It is the third expansion pack for "Half-Life", and like its predecessors, "Decay" returns to the setting and timeline of the original story, albeit portraying the story from the viewpoint of a different set of protagonists: two women scientists working in the Black Mesa Research Facility.
 "Decay" is a cooperative multiplayer game, designed to be played by two people working together to pass through the game's levels.
MapCore is a game development community with origins in "Half-Life" mod production, which since its inception in 1999 has evolved into a thriving forum featuring all flavours of game development including level design, modelling, concept art, and programming.
 With 100+ members part of the professional games industry working for the likes of Blizzard, Crytek, DICE, Gearbox Software, Rockstar Games, and Ubisoft, MapCore offers an opportunity for professionals and amateurs alike to socialise, learn, teach, and find talent.
Half-Life: Opposing Force is an expansion pack for Valve Software's science fiction first-person shooter video game "Half-Life".
 The game was developed by Gearbox Software and Valve Corporation and published by Sierra Entertainment on November 19, 1999.
 "Opposing Force" is the first expansion for "Half-Life" and was first announced in April 1999.
 Randy Pitchford, the lead designer on the game, later noted that he believed Gearbox was selected to develop "Opposing Force" because Valve wanted to concentrate on their future projects.
 Over the course of development, Gearbox brought in a variety of outside talent from other areas of the video games industry to help bolster various aspects of design.
Vivisector: Beast Within is a Ukrainian made first-person shooter game released in Europe in 2006.
 Inspired largely by the movie "Island of Lost Souls" and the story "The Island of Doctor Moreau", which the movie was based on, the game is set in 1987 on a covert military installation on Soreo Island, where a riot has broken out by renegade geneticist Dr. Morhead's experimental human-animal hybrid soldiers against the corrupt general that ordered their creation.
 It is the player's job, initially, to help the General suppress the riot and regain control of the hybrid soldiers, but the player eventually switches sides against the General halfway through the game.
 The game is most infamous for its "vivisection point" feature, which allows the player to rend an enemy's flesh from their body with each shot (though, due to Germany's strict censor laws, this feature was removed for the human NPCs).
 This game came out of the cancelled "Duke Nukem: Endangered Species Hunter" title.