|Think about Loose Coupling|
I don't think it matters if someone puts a copyright notice or not. Like in this older thread I still think one has to assume full copyright and no license, unless stated otherwise. That means, you'll have to ask permission to use/ distribute code.
With the growth of perlmonkscode the chance of some code getting commercial deployed becomes larger. So my $0.01 (e0.01 also fine) would be: "ask the author". If you really want to use code from someone else for code reproduction, you'll just have to ask nicely. And come to terms. Probably most ppl here would agree on a GPL/artistic license. (update: like tilly says, you can always apply licenses afterward)
(disclaimer)....but I have been away for a while, maybe attitude has changed too much....
In reply to Re: Copyright of code on Perlmonks; and commercial code