Is Roald Dahl still alive? He probably sold the rights to his books.
He's dead, but the author's estate inherits the copyrights.
But the author's estate likely agreed to the changes.
Dennis Wheatley was a popular English occult novelist, whose books no longer hold modern views on race. They were recently republished with changes "with the permission of the author's estate."
I remember reading his book, The Satanist (1960), in the early 1980s. I was surprised that it contained a passage in which the heroine was described as "having any normal white woman's aversion to sexual relations with a colored."