I have some for paper plane masking and mine is matte (well, sort of semi-matte pearl) - used it forever in pre-mac graphics arts, and don't recall ever using gloss. The ruby tape was glossy though. I think the stuff is matte so you can sketch lines on it with a pencil?
For darkroom/B&W safety - yep, red seems to be red. I use red spiral party bulbs in my darkoom, 2 of them in metal reflectors bounced off the ceiling - it's like daytime in there, but no fog. I mean, it's scary-bright for a darkroom!