All the programmers came from the Dynamic Modelling Group at the MIT AI Lab. Originally, "Zork" was a name that any unfinished program around MIT got. When the game was finished the implementors called it Dungeon, but people went on calling it Zork, so the name stuck (not an unusual course of events for software and other high-tech products with entrenched "working titles"). Other names introduced in the Zork universe are grues and zorkmids.
The company Personal Software produced a version of Zork I (roughly the first third of the original Zork) for the Apple II and TRS-80 home/ personal computers in 1980. The programmers managed to fit very rich complexity into the small personal computer systems of the time, and gain portability between them, by using a specialized "game engine" called the Z-machine. Personal Software had plans to release Zork II as well, but never got that far.
Finally Infocom, a company started by the above people and others with the intention of producing adventure games brought out versions of Zork for most popular computers of the era, such as the Commodore 64, the Atari 8-bit family, and the IBM PC, in addition to the above. Each game came on a 5¼" floppy disk, with the game engine getting loaded into computer memory at startup, reading relevant parts of the game data (scene descriptions etc) into memory during gameplay.
Zork and its relatives fit into a category known as interactive fiction. Zork, like the other Infocom games, distinguished itself in its genre as an especially rich text adventure, both in terms of the quality of the storytelling, as well as the sophistication (at the time) of its text parser. The parser understood full-sentence commands ("attack the grue with the egg") that went well beyond the simple verb-noun commands ("attack grue") that were the standard fare of the day.
The original Zork Trilogy: