Short answers, pulled from the story.
ASCII released 2D Fighter Maker 95 in 1995 to allow users to create their own fighting games. This program enabled users to import their own graphics, sounds, and entire characters to build games without needing a team of artists or programmers.
MIRAI from the U.K. band INTELLIGENTSIA is the real-world musician included as a playable character in the 3D Fighter Maker for the PlayStation. The band composed the game's music and created the in-game sound effects while MIRAI received a fully realized move set and animations.
The 2D Fighter Maker 95 engine became a cornerstone of the M.U.G.E.N. community after ASCII exited the gaming industry. Fans modified the software to create diverse games including role-playing games, platformers, and visual novels while distributing pirated and fan-translated versions globally.
2D Fighter Maker 2nd failed to achieve the same global popularity as the original 2D Fighter Maker 95 due to the large amount of M.U.G.E.N. communities already in operation and the incomplete translation of the FM2K software and documentation. The software remained widely used by dojin communities in Japan but never reached the same level of global popularity.
Kadokawa exclusively licensed the 2D Fighter Maker 2nd engine to exA-Arcadia in 2019 to re-develop the engine from scratch for hardware rendering. This new version included features like 16:9 widescreen and 0.3 frames input latency but was only available for exA-Arcadia developers.