You can’t sever the asset and the obligation in this case because royalties are contingent on licensing the author’s intellectual property. With no licensing agreement, there is no asset.

On the other hand, the only wrinkle that might make this interesting at all, is the fact that all the works in question are novelizations of others work, for which either Alan Dean Foster himself had to license or created at the request of the licensor. I don’t think that materially changes things but then I’m not paid like a Disney lawyer.