The ongoing hassle with APNG

The SeaMonkey throbber image, a rounded animated image of bubbles rising up in front of the SeaMonkey logo, is still a GIF, even on trunk. Therefore, it doesn't look too good on the non-alpha-transparent rounded borders when using a dark background, like here:



(This is showing the still version, which is just a non-animated copy of the first frame of the animation, so that the transition to the real animation is smooth.)

I've meant to look into this for quite some time, and now, a bug was filed for this (the image above is a screenshot attached there), so I came to think about it once again.

The obvious alternative is to use an APNG image, which is supported since Gecko 1.9, see this article about better animations (also using a throbber as an example, btw).

But here comes the problem: Even though APNG now has a project website and apparently even an APNG campaign, we still don't have a lot of tools I could use to create our animated throbber. The list of applications that work with APNGs isn't very long, the four application apparently capable of editing APNGs are two closed-source Windows/Java apps and two add-ons, one for another Java app I don't have and one for Firefox 3.
Apart from all those just being animation assembly apps and not image editors, I can't use any of them in my usual workflow, I don't even have Firefox 3 installed, I just have SeaMonkey trunk and Minefield trunk. The latter might work for dolske's APNG Edit Add-On, the former doesn't, as I saw when even trying with an install.rdf hack and a slight overlay change last time I tried (which was some time ago, when it was still pretty new).

Now I have been through all this discussion around MNG and animated alpha-transparent images that lead to the creation of APNG, and yes, MNG is probably an ugly spec while APNG is right to the point of what we want, sure. But this continuing lack of tools doesn't help. I'm usually doing all my imagery design with the GIMP, and this as well as a large number of others support saving animated GIFs as well as MNGs but no sign of APNG there (not even in the very current 2.6 version I have here).
So if I even get this Firefox Add-On to run that seems to be the "best" option, I need to create single PNG frames with the GIMP, assemble them with the Add-Ons, test them, go back to the GIMP for adjustments, re-import the changed frames with the Add-Ons, and redo those steps until it works. Not the ideal way to do things.

I just hope this format gets adopted by major editors or I fear all we'll have in our Mozilla source will be a format that is even more dead than MNG - which is clearly not what we wanted. Let's see if I can get that throbber done at least - I don't even know if I have anything better than those GIF frames as originals, so I might need some amount of heavy tweaking there.