media-gfx/apngopt has this (incorrect) description: extract PNG frames from an APNG This description is the same as media-gfx/apngdis package, and probably apngopt ebuild was based on apngdis. The "correct" description should be something like "APNG Optimizer" (which is the text found in readme.txt)
http://sources.gentoo.org/media-gfx/apngopt/apngopt-1.0.ebuild?r1=1.2&r2=1.3