Yes, rabbits are herbivores. (And the "No Meat-Eater Poo" rule is a good one.)
I've "baby-sat" pet rabbits for a couple of friends in the past, but unfortunately it was during the gardening hiatus, so I learned about rabbits but didn't get any "good stuff."
I sometimes donate off-the-wall supplies to the local rabbit rescue whose "waste" I tried to compost last year. They LOVED the organic carrot tops last week! (Well, the people
said the bunnies
would love the carrot tops....) "Rabbit food" as a synonym for "salad" makes sense if you see the fresh foods the bunnies have: leafy greens, carrots with tops, etc. They also eat prepared rabbit "kibble" whose make-up I don't know.
The difficulty I had with the rabbit waste last year--and the reason I'm not going to pick up any more of it from either rabbit rescue group--is because, even though the poo itself degraded quickly and completely, the timothy hay and the litter absolutely did NOT compost.
I began picking up rabbit waste last March and stopped in June. In August, I could still discern the litter. It was white, fluffy stuff, perhaps based on cotton fiber or newspapers? The timothy hay was completely intact, too.
In December, the litter had begun to disintegrate, but it was still distinct from neighboring ingredients in my compost pile (kitchen peelings, leaves, what-not), even after I turning the BioStack in August and December. The hay was still completely intact.
A week ago, DH and I turned the BioStack. The rabbit litter was--after a minimum of 9 months and, for some of it, a year--at last
decomposed. The hay was *mostly* decomposed, although there's still a good deal of recognizable hay.
So my take on it is:
1) 100% "pure" rabbit poo = a compost "green"
(nitrogen source). Unless you have your own rabbits, I can't imagine how you would lay hands on such 100% stuff, but it would be terrific!
2) Rabbit litter = a very slow compost ingredient
, so slow that it won't help for anything but aeration, so its green vs. brown status is irrelevant
3) Rabbit hay
= almost as bad as peach pits, i.e., it *may* work *if* you have a nice, hot compost pile. I don't; I have a cool to cold pile, for a number of reasons. I would classify timothy hay as a very s-l-o-w brown
(not a scientific term, but it's definitely acting like wood in my pile).