I knew @mjd long ago as part of a small group of us into #Perl & also hard-core academically-minded programming language theory. MJD & I fell out of touch in 2000s. Even back then, I'd've urged anyone to hire MJD if they could. A quick look of his current resume…
https://plover.com/~mjd/cv/Mark%20Jason%20Dominus.pdf
…shows MJD spent last 20 years becoming even more knowledgeable in all areas of software.
I made this public job reference for MJD completely unsolicited. I hope you'll hire him to work on 100% FOSS, of course!