freefonts URL: https://download.gimp.org/pub/gimp/fonts/freefonts-0.10.tar.gz
I came across an old bug related to this (http://gnats.netbsd.org/40609) I am most certain about strcasecmp, that's what another utility does.
extrabold -> extrabold seems reasonable.
Less sure about Plain, in the sense that I don't have a reference standard to point to. It seems common among font-handling to handle "plain" the same as "normal" or "regular" (weight 400).