Although I doubt anyone remembers these characters, they are probably, technically, under copyright, owned by the Bantam-Dell Publishing division of Random House Books. It would definitely be cool if the post-1962 Dell characters were PD, but there are only two ways they could be.
Anything published after 1962 had its copyright automatically renewed and these guys were published in 1967. That means the copyright will last 95 years. So there are only two ways that these comics could be PD:
1. If there was not a proper copyright notice on these books (Super Heroes #1), then the characters would be PD. But you would have to check a copy of the comic to determine that.
2. It is possible that the ownership of the intellectual rights to Dell Comics (which were highly unsuccessful after 1962), were not explicitly transferred to Random House when they bough out Dell. I doubt an unsuccessful comic line of only a few issues was a big concern in drawing up the agreement, but there could have been a general, "all intellectual property" kind of clause, that could be used to argue ownership. If the rights were not transferred, then the intellectual property in these comics might be considered "orphaned" making them, effectively PD.
If you can find evidence of either possibility, let the rest of us know!
Subject: The Fab Four 
