This game is a version of UNIX Rogue 5.2.
After the success of Rogue 3.6, Michael Toy, Ken Arnold, and Glenn Wichman further modified the game. Version 4 made some interface improvements and tweaked many numbers. In April 1982, version 5.2 was completed and distributed with BSD. It is called V4 because it has more in common with the previous 4.x releases than with the 5.x versions which followed it.
The Roguelike Restoration Project obtained a copy of the source code, probably from an FTP site that has since shut down. The game was updated for modern computers in 2005. The RRP called its latest build "5.2-1", and made a few source changes between then and the end of development in 2008.
The Roguelike Gallery's version includes further bugfixes and compatibility improvements. Gameplay remains true to the original.