libpng
on SourceForge
libpng16/older-releases/1.6.20beta/libpng-1.6.20rc01.tar.gz
libpng15/older-releases/1.5.25beta/libpng-1.5.25rc01.tar.gz
libpng14/older-releases/1.4.18beta/libpng-1.4.18rc01.tar.gz
libpng12/older-releases/1.2.55beta/libpng-1.2.55rc01.tar.gz