right now these values are hardcoded within the app. for example, the test for the afdko seems to be whether or not the binaries show up in the adobe-recommended ~/bin/FDK/Tools/osx
ttfautohint is a bit more mysterious (i can’t figure out how to get it to enable the ttf autohint checkbox to work even though mojo.compile.hasTTFAutoHint returns true for my version of ttfautohint installed via homebrew).
regardless, it would be easier to debug this behavior if these search paths were easy to set. i think the current behavior probably satisfies many common-cases, but i suspect that there is wide variability in the location of sundry binaries.
It is indeed recommended for FDK to be installed on a specific path.
For ttfautohint RoboFont is checking it with which ttfautohint terminal command to see if it installed on your local machine. In a normal setup it should be something like /usr/local/bin/ttfautohint
Next to be installed ttfautohint requires an ‘o’ glyph in the font otherwise it just fails to autohint. (see ttfautohint -h)