"that restriction has been removed" and "the terms of use of each DLC ... are the same as before.
I don't read that. "that restriction has been removed" is referring to "materials
included in the RPG Maker series were previously allowed to be used only in the RPG Maker series," emphasis mine.
So any assets you got from purchase of an RPG Maker engine (the RTP) can be used with any other game making software you own.
Only Unite related DLC has an update with its terms of use" are contradictory.
It says "The terms of use of each
DLC produced by GGG are the same as before" (emphasis again mine). So assets you purchased
outside of the software, DLC, are
not free to use in other game makers. Only the RTP that came with RPG Maker itself.
The part you quoted indicates that DLC for RPG Maker Unite
will have terms of use allowing it to be used in any software, like its RTP.
And by "in Unity" do they mean "in Unite" or can you use MZ materials in Unity if you're not using Unite?
Correct, I read "in Unity" as an example for any other game making software. It's just a bit confusing that they chose that example when they just released RPG Maker Unite.