How to read Fireworks PNG multilayer files without Fireworks

PNG files do not have layers, so Fireworks layers are stored in the private chunks of the PNG files in a proprietary format which is not PNG. I don't know of any program that can read them. You'll need to ask the owner of these photos to convert them to flattened png (mono-layer) or into another multi-layered format such as psd.

If that's not an option, my only advice is to download a trial version of Adobe Fireworks (registration required) to convert these photos.

You can save from any Adobe Fireworks you have at your disposal, and save with a GIMP .psd and so can at least detect the layers of your archive.

You can move objects and text layers, but with text layers you cannot modify the text and keep the same format, only by deleting and doing it using the GIMP text tool .

I am using Adobe Fireworks CS5 and Gimp 2.4.0 for testing.

Well, if you just need to read these files you can use Batch PNG to JPG to flatten them. It includes a Preview which allows you to actually look at the PNGs if that's just what you want. But if it is animated it will only export the first frame.

So,

XnView viewer, fully supports APNG
Firefox browser, too
ImageJ image processor, too

Meanwhile I noticed you came from Stackoverflow.com. If you need to programmatically access this format, you will need a patch for libpng that gives you support for APNG. It's an excellent (albeit, slightly non-standard) addition to libpng if you need it. It's after all what all the above applications use. ;)