Is it legal to use gimp to manipulate copyrighted images?

[Techwing]

Technically you need a license from the copyright holder if you modify images and put them on Facebook, although in some cases it may qualify as fair use (if it's a parody, critical comment, etc.). If you heavily modify a copyrighted image for purposes of comment, education, parody, etc., and then put it on Facebook, you probably won't be sued. The more heavily you modify the image, the safer you are.