confused about the png/APNG issue

[david coder]

one thing i don't understand about what otherwise seemed to me the best
suggestion for dealing with this issue:  assuming that "the system png"
refers to the png that comes w/ the freebsd distributions, how would
upgrading the png port help?  wouldn't the other ports continue to use the
system png?  there was, i know, a hint or two that upgrading old systems was
a necessary part of the fix, but then why would the port matter @ all then,
ie, why wouldn't updating the system be sufficient?

obviously, i'm confused.  will some patient person please explain where i'm
going wrong?

david coder