GD Map is described as 'GdMap is a tool which allows to visualize disk space. Ever wondered why your hard disk is full or what directory and files take up most of the space? With GdMap these questions can be answered quickly. To display directory structures cushion treemaps are used which visualize a' and is an app in the os & utilities category. There are more than 50 alternatives to GD Map for a variety of platforms, including Windows, Mac, Linux, BSD and Homebrew apps. The best GD Map alternative is WinDirStat, which is both free and Open Source. Other great apps like GD Map are WizTree, Baobab Disk Usage Analyzer, TreeSize and SquirrelDisk.
Fast flexible, but not actively developed anymore as it seems to me.