The pngalpha.library has been re-assimilated again for the icon.library 46.4.218, even though I would really prefer to live without it. But unfortunately, I discovered some icons with a fixed background color predefined in the PNG file already which gets in conflict with my method of extracting the alpha information by comparing two different colored instances of the same image. Some of these icons are included in the Crystal_Clear_Amiga collection, but most of them are part of emailware packages. I got only a few of them together with a bugreport. Of course, the installation of the pngalpha.library is still optional as before.
Update: http://aminet.net/package/util/libs/IconLib_46.4