This is a biggie!
It is my understanding that when WESTERN PUBLISHING split with DELL and eventually with GOLD KEY, that they failed to renew copyrights on their own material and let it u[p to owners of individual copyright owners to do any other renewals. This is why DELL FOUR COLOR is able to be used by others.
The also places the back-up features and text pages which have the WESTERN PUBLISHING copyright notice into the public domain (I think). This would include things like MABU, BROTHERS OF THE SPEAR, and TWO AGAINST THE JUNGLE which were WESTERN PUB back-up features in TARZAN.
BROTHERS OF THE SPEAR is pretty well known, but the other two are not. These two I would like to make as compilations and maybe they would be acceptable here as public domain or orphaned items.
Don