Here's a short relevant Reddit thread:
https://www.reddit.com/r/firefox/comments/9uemks/greasemonke...
Though I wrote Greasemonkey originally, I have no idea regarding the answer to this question. What I can say is that Anthony Lieuallen is a super standup guy, which is why I handed it over to him and Johan way back. Based on that alone, I personally continue to use GM whenever I have a need.