YIMBY is the opposite of NIMBY. “Yes In My Back Yard” Basically people that are for HUD/affordable housing development, for rezoning from single family to multiplexes, etc.

NIMBY means Not In My Back Yard, so YIMBY says stfu yes, you.

And the article does say that in fact.

“At the same time, Green’s sweeping invocation of executive, emergency powers—a sort of “yes in my backyard” (YIMBY) martial law—is provoking concern from an equally bipartisan group of critics.”