Thanks always to Tim.
If you do hunter-gathering on web palettes, you find most of the images you might want to use as GIMP color resources are not indexed and are not organized in grids and making palettes from them can be tedious. With Tim's script you can sample gradient images with alarming ease:
This works well with, for example, color temperature gradients and hue-based gradients. Similar colors can simply be deleted with the PALETTE EDITOR. Or, as in the whites above, retained for their visual framing value.
If the source image is organized but has text it can be pre-processed in a few strokes and clicks. Text (such as color names or RGB values) placed over the individual colors can be cleared up with the clone tool or Resynth HEAL SELECTION or select-and-delete followed by ZEALOUS CROP to close the gaps.
If there's any further development interest in the script, in my opinion it would be useful to have a variable sample area to use for source images less well organized than gradients. Such as paintings or photos. Some [well, at least one] "natural media" painting programs offer this feature as part of their [its] palette-making.
And, for myself, to close the circle, it would be nice to have the current output also export into a new image. Perhaps as a grid instead of HTML. There already may be a script or function to do this directly, but I haven't found it yet. Still new at GIMP and still hunting.
GIMP Learn rocks...