I've always understood the rule as "unless you buy or are given a keg directly by a brewery, it is still technically the property of the brewery, regardless of how you come into possession"
My point is that if they decommission a keg, I believe most brewers discard them, not spend time/money marking them to give away to the homebrewing community. I would just approach your local brewer and inquire about obtaining one of their kegs.
perhaps a line of single hop IPA's - there's so many new hops out there!!!