Please note that there are no guarantees that XPI installations will work in advertised minVersion and maxVersion. Farby did include some basics for SeaMonkey however a few things seem to be missing.
The current HEAD here will probably not work directly in Firefox and nor should you be using this fork in Firefox. It is intended for SeaMonkey users only.
Announcements at https://openuserjs.org/announcements/Greasemonkey_Port_Update
When can we expect an update to the latest Greasemonkey and a sync release with it? or at least a few weeks later. I'm having problems excuting some scripts for OGame.org. Working OK with SeaMonkey 2.33.1.