STHUD information can be found here: http://dslyecxi.com/?p=8
STGI is here: http://dslyecxi.com/shacktac-group-interface/

Usage of STHUD or STGI requires agreement with the following terms. The mods (STHUD/STGI) may NOT be modified, included in other mods in whole or part, used for military training or any commercial purposes whatsoever, without prior permission from the authors (zx64 and dslyecxi). Redistribution of the addon via 6updater/PwS etc is permitted only if it is unmodified and free of charge. Modifications are forbidden without prior permission from the authors.

You can reach the authors at dslyecxi@gmail.com