This is a port of the Xtract program to macOS.
The original Xtract Copyright (C) 2000 Timothy Hale and Mathieu Olivier, licensed under the GPL, hosted on ReBUILD Project.
It goes well with the great Blender Add-on for importing BUILD engine maps.
xtract <grp file>makeMap extraction was reverted to the native with small changes (it now extracts to maps/ instead of the current directory).
The original xtract used dukeconv, this code has been isolated under DUKECONV
define. If you want to use dukeconv, build it with make DUKECONV=1.
You can get the dukeconv.exe from the original xtract archive by downloading
it from the original page.
--- xtract readme---
This program is designed to extract the palette.dat file, any art files, and any maps in a build engine group (grp) file.
It is packaged with the dukeconv program, which will convert all your build engine map files over to the intermediate map format used by Quake 1/2 and Half-Life.
xtract will extract all the art from a build group file, and place them in a subdirectory named tiles. It will then Extract all the maps, and the dukeconv program will convert them, and place them in a subdirectory named maps.
After this you will need to put all the tiles in a wad:
http://prime.telefragged.com/wally/
Links you to wally, a very capable wad maker.
After this, you should be able to make your own maps using the extracted maps as a starting point.
Enjoy!