the existing OpenType files have problems in X11, but the TTF files work A-OK....

[robohack]

It should probably be noted in the install instructions that the TTF files are strongly recommended for X11 as the OpenType files will not work with all X11 applications, especially older ones like xterm, or indeed even with some like Emacs when it is run from a remote server.

Also the X11 install instructions should mention that the directory the files are copied into must already be in the server's font path (see xset q) and that the following commands are also required to be run in that directory:

cd .fonts && mkfontscale -o fonts.scale && mkfontdir -o fonts.dir && fc-cache && xset fp rehash