Kroz is a series of Roguelike video games created by Scott Miller for IBM PC compatibles. The first episode in the series, Kingdom of Kroz, was released in 1987 as Apogee Software's first game. It was also published on Big Blue Disk #20. Kroz introduced the scheme of the first episode being free and charging money for additional episodes, a technique which defined the business model for Apogee and was adopted by other MS-DOS shareware publishers.
The games were discontinued in 1999. In March 2009, the whole Kroz series was released as freeware by Apogee, and the source code was released as free software under the GPL-2.0-or-later license.
At the same time, Miller, looking for other avenues to distribute his games, turned to the shareware model. Shareware was distributed freely through bulletin board systems (BBS), where the boards' users made voluntary donations. Since shareware was not very profitable at the time, Miller developed a variation of the shareware model, dubbed the "Apogee model", in which only a fraction of the game would be made available to play for free on BBS. The game, upon completion, would display Miller's mailing address to the player and ask them to contact him to pay for that game, which would allow them to buy the rest of the game's "episodes". This shareware version of Kingdom of Kroz was the first game to bear the name of Miller's one-man company, Apogee Software Productions. before becoming the shareware episode of the second trilogy of Kroz games, the Super Kroz Trilogy.
In 1990, an enhanced version of Kingdom of Kroz was released as Kingdom of Kroz II, which became the shareware episode of the series as a whole. Kingdom of Kroz II was different from the original version, and incorporated 21 different levels, many of them from later games in the series, especially from The Lost Adventures of Kroz. The original Kingdom of Kroz I stopped being distributed as shareware, but was still available commercially, and was then marketed as the third episode in the series, with episodes two and three moving up one place. For a time, the series consisted of seven commercial episodes (including the original Kingdom of Kroz I), plus an enhanced version of one of them (Kingdom of Kroz II) distributed as shareware. During this time, to be able to buy the commercial episodes, the shareware episode had to be registered first.
In 1991, the other two episodes of the first trilogy were enhanced to their "II" versions, and the original Kingdom of Kroz I stopped being available, being replaced by its enhanced version.
Source code
At one point the source code for Kingdom of Kroz could be purchased for $190, Return to Kroz for $350 and The Lost Adventures of Kroz for $950. Later the source code of Kingdom of Kroz II was for sale for $400, Return to Kroz for $300 and The Lost Adventures of Kroz for $500. By 2009, the source code was released under the GPL-2.0-or-later license.