Both upstream authors agreed to the license change.

From Jason Lotito <jasonlotito@gmail.com>:

  "Any code I contributed can be released under the LGPL 2.1, or later,
  as needed to make it compatible with Image_Graph and Image_Canvas.

  Jason"

and from Andrew Morton <drewish@katherinehouse.com>:

  "Sounds like Jason's on board and since he's contributed the majority
  of code, I'd be happy to relicense any code I contributed to the
  project.

  andrew"
Signed-off-by: Francois Marier <francois@catalyst.net.nz>