The rule I always heard when I was a kid was if the month had an "r" in it, rabbit was safe for the plate. So based on that, Sept-Apr should be good to go. With that said however, I doubt I'd trust that logic unless I heard it from a more reputable source that as an old wife's tale. As I recall, the only times I ate wild rabbit (it's probably been ~30 years since) were in the Jan-Feb time frame.
I'd be interested to hear others' thoughts as well.