Well I gave it a go. FWIW, herewith my review of (what I shall call) the Korean tool:
1) You have to do the work in a separate, smaller window - very hard to see exactly what effect the sliders are having until you apply them, check the main Paint window, and then go back to the small window. Not conducive to intuitive editing.
2) The ridiculously complicated numbers accompanying the mysterious sliders might mean something to gifted people, but they mean nothing to me.
3) (Most importantly): I only spent 3 or 4 minutes with it, but I could only get the thing to make pincushion manoeuvres. The problem I have is with a lens that curves edges in, a little - I don't need them more curved in. Perhaps the tool can barrel as well - I'd certainly hope so - but if you can't see how that's done after a few minutes investigation.... YMMV but I'm deleting it.
On the other hand, the tool I got via Softpedia is incredibly simple, immediately usable, and seems to do the job - in both directions - very well (I may be a computer idiot, but I can get very fussy about straight lines ; )