Ask here, I'd reckon.

Any number of songs that are traditional and in the public domain have been subject to attempts by people to copyright them; so the fact that a song appeared on a list of copyright songs, even with a name and date attached, wouldn't necessarily mean much.

But if you set up a thread here asking the question about a particular song, you've got very good chance of finding out the true facts of the matter. (Such as that a particular arrangement is copyright, but that other versions aren't.)