As I clicked submit, MaxSt also posted!

@mahvin, try this:
1) right-click gif2apng. On shortcut menu, select Properties. On Permissions tab, set as executable.
2) (with test.gif and gif2apng in same directory, as I did for my test run) use this as your command line:
The <period><slash> tells Linux that the program is in the current directory.

To test I downloaded your gif of the candle, wine bottle, and glass. Keeping in mind that I do believe my png library is still borked, I ran your gif through the conversion program then opened the output in Gimp to see the layers. The layer names as I got them:
Frame 12 (180ms)(replace)
Frame 11 (180ms)(combine)(!)
Frame 10 (180ms)(combine)
Frame 9 (180ms)(combine)(!)
Frame 8 (150ms)(replace)
Frame 7 (150ms)(combine)(!)
Frame 6 (150ms)(combine)
Frame 5 (150ms)(combine)(!)
Frame 4 (130ms)(replace)
Frame 3 (130ms)(combine)(!)
Frame 2 (130ms)(combine)
Background (130ms)(combine)

Because of my bad png library, I got a questionable output, with transparent objects on the tabletop. I was able to see the animation in Gimp Filters>Animation>Playback, but trying to view the output in Firefox mad the whole apng flicker off and on. So since you have a good png library, try my steps above.

This is the result of the larger gif (one problem is, I inadvertently deleted the xcf, or failed to save the xcf) and now the larger gif is stretched out. But for file size comparison, it's most interesting (495k versus 959k):

YIKES! Had the same problem (transparent layers) you did, Bob. But at least it converted. Thanks to both of you for helping me understand the ./ command (I would have never thought to do that).

On another note: using the other converter (gif2png) it saves each gif layer to a separate .po1, .po2, etc. I'm clearly not understanding how to use the converters via command line. I tried to drag and drop in Ubuntu and it doesn't do anything.

In Ubuntu, I have a group of files that I want to be able to use in any directory, so I have them stored in my home/bob63/bin directory. This directory is on my path. Then while in nautilus, I can right-click within any directory and choose Open in Terminal from the shortcut menu. When the terminal opens I can just type in the program name followed by any command-line options and file names. This allows me to omit the <period><slash> from the command line.

As far as deleting or forgetting the xcf - what if you open the gif in Gimp then save it as xcf? That would give you back your layers, right?

Bob:

What does "this directory is on my path" mean? Please excuse my ignorance, I'm a 4 month old Ubuntu noob.

The thing with the gif is that its already stretched and looks awful, I would need to start all over from scratch and not save it as a gif animation.

Gawd, look at me go off topic on my own thread. But hey, if there is anyway to salvage png conversions, I'm looking for it. People do like using animations as avatars, and lossless png animations are enticing!

From what I have experienced using gif2apng, it's not liking the gif data. It's messy and splotchy. But creating apng directly from gimp, well, they look good but are huge in size.

@mahvin, Sorry, I was unsure of your level of experience.

A "path" is the method Windows and Linux (I'm not familiar with the Mac OS) operating systems use to locate files - particularly executable files - within the file system. Under these systems, there is a variable within the environment which lists the directories which the operating system is permitted to search when the executable is not in the current directory.

I'm using LinuxMint 9, a distribution that is based on Ubuntu 10.04. My path environment variable looks like this:
This tells the OS when I type an executable name in the command line (not a built-in OS command), to first look in the directory /home/bob63/bin. If the file is found - and assuming the permissions are proper - execute it; otherwise, look in the next directory on the list, etc. Note that the directories are colon-separated.

To see what your path looks like, open a terminal and type printenv. I suggest having the terminal window maximized, as some of the output may wrap on the screen and could be confusing. If you are interested in setting up something like this post back (or send me a PM if you don't want to add to the OT-ness )