This just converts files to psf format with freetype, nothing else.
ttf2psf -g -c [charset file] -e [equivalence file] input.ttf output.psfu.gz
See ./data for common charset files and equivalence files.
This specific utility is released under the GPL-3.0 or later license, but there are several other projects with other licenses that this one wouldn't have been possible without.
The charset and equivalence files are taken directly from Anton Zinoviev's bdf2psf utility, which is released under the GPL-2.0. These specific files are in the public domain, but I feel like I should include this message.
To write this program I've had to consult Alexey Gladkov's kbd utilities quite a bit (GPLv2 or later). I haven't copied any code from them, but I feel like they deserve some recognition.