We've just taken down the GIMP and Inkscape animation editor features from the stretch goals. We've decided if we are going to do these they can't be little hacks we make on a small budget. We'll be reaching out to the core GIMP and Inkscape teams and putting together new and properly laid out projects to implement animation editor support. For example in the GIMP we'd want separate layer stacks for each frame and in Inkscape we want onion-skinning and tween animation. These are things that we would just not be able to implement on our own with such a small budget.
We understand many of you had probably put money in specifically to try and hit these reach goals. Please know that as far as development costs go we're already spreading ourselves pretty thin. Rather than promise something only to end up without proper funding and providing a poor implementation we'd like to do it right. Besides, realistically it does not look like we would have come close to either goal. We hope you understand.
Also please keep in mind that part of the core of this project is creating a cross platform GUI for apngasm. You can still save individual frames in the GIMP or Inkscape and use them to create APNG animations.
Thanks again for your support. We sincerely hope you will understand our decision.