The Pale Moon devs weren't super polite about it, but they were objective and clear in their statements.
The weren't super polite. In fact, they weren't polite at all. They were rude and demanding. I can't blame anyone for not wanting to collaborate with them after reading that thread. I wouldn't.
Well there were 2 "issues" in that case. Being right about one certainly doesn't justify the other. One was the "technical" one of the conditions of redistribution. The other one was that one guy decided to start off the discussion as a grade A a-hole, rude, arrogant, dismissive, confrontational, and probably a few more. Discussions can degenerate but how often is it productive to start one with such a hostile attitude, especially in public?
Right as he may have been I wouldn't touch such a toxic person with a 10-foot pole. Such an attitude sabotages any amount of skill until the net contribution is actually lower than that of a less skilled person you want to work with. Case in point, so many devs actively stay away from the project (or more likely the person).
That thread burnt most of my goodwill toward Palemoon which wouldn't have happened if they'd at least approached them civilly in the first place. Even if it had escalated from there.