Reasonable path forward. I was fond of the lowkey color symbols signifying target application prior to 28.11, but I can imagine people overlooking them and blatantly installing 5 year old Ff extensions and then being stumped when they misbehave with their 2 week old UXP browser. I'd say the shade of yellow conveys the message more clearly
Now what I'm wondering about is the next major version, presumably 29.x. Can one assume the dual-GUID system will be dropped at that milestone? If a legacy Firefox extension by grace of shared ancestry works apart from the targeted application, then the only work necessary for a potential forker
in the short term is to change the GUID to target Pale Moon?
Of the 17 extensions I use, only 2 were acquired from Classic Add-ons Archive. Really stoked by the amount of Pale Moon-specific add-ons accumulated over the years. Kudos to all those involved.
Off-topic:
I've returned after a hiatus from Firefox. I got depressed after updating every ESR and noticing more and more XUL deprication, resulting in browser elements looking increasingly more like a webpage, adhering less to the system theming. That and the HTML add-ons manager and configurations editor did it in for me. Aris's customjs and customcss scripts work wonders, but I have serious doubts about the future. The fact userChrome styling has to be unlocked from the configurations editor kind of has it marked for death, I would think.