So, why can they publish it now? His death doesn’t nullify the agreement, does it?
Dead people have no right to privacy in law as I understand it.
Not a lawyer, not in the economies involved in this.
"it depends"
Grim reminder to better control privacy while we are still alive.
It seems he contributed, so I assume otherwise.
Copyright generally lasts 70 years after the death of the creator or after the first year of publication, depending on the type of material and/or when it was first published: Artistic works, including photographs, Dramatic works.
https://copyright.unimelb.edu.au/shared/basic-principles-of-...
And dead people don't have rights past what they have decided on inheritance and even this can be sometimes overturned by justice. This is the reason wealthy people sometimes give their wealth to a foundation but if the foundation doesn't find a way to make it sustainable and money runs out it also ends up dissolved regardless of the cause it was bound to serve.
But without seeing the contract, we don't really know. Perhaps it only bound the original publisher, and not the author, but some other contract had bound the author to only publish through that publisher, and that publication contract is no longer in force. Who knows, the article doesn't tell us.