I think the Daemonhunters codex is still valid in friendly games, however it is no longer legal in tournaments, and I would therefore say it is not legal in competitive games, either.
Just because the rule doesn't apply any more doesn't mean that the old codex is still valid, and just because a codex replaces another doesn't mean that rules that applied to the old one apply to the new one. There is no basis in rules or history for either assertion.
The "official" validity of a codex is determined by GW saying it is valid or not for their tournaments. The "friendly" validity is determined by your opponent being willing to play against you with it or not. If you don't know, it is generally good form to use tournament rules, so people don't get surprised.