And apparently there is at least one guy using it to draw illustrations[1] and explain how to use it with a tutorial[0].
Sadly the site seems to have been moved from another location and the obj files (the files tgif uses) did not survive the move. Only one file was transferred from another tutorial (in Japanese) about using Tgif with Gimp, most likely because it had a "wrong" extension (.html). It does open fine in a build of Tgif i just did though[2].
Well found ;) I remember crossing this multiple times since the 90s while looking for Tgif-related info, but always in Japanese I think... and every time with marvel for his technique applied with both excellent software.