Similar programatic abilities can be found in the following window managers:
- wmii - via the 9fs interface - https://wiki.archlinux.org/index.php/wmii
- ion3 / notion - via lua bindings - http://notion.sourceforge.net/
- guile-wm - similar goals as stumpwm, with scheme - https://github.com/mwitmer/guile-wm
Of all of these notion is the most "out of the box" complete WM, whereas guile-wm is the most immature.