Here is a thought experiment.
Change all the names, the characters, the places, the titles of people, ei: the one power = the source, aes sedai = wiccan, anything with a name is changed.
Now do you think RJ's estate would be able to sue Amazon and win for stealing the WoT story if they did not own the rights already?
I do not, the story for the show has no real connection to the books without the names, it could be argued it was based on any number of badly written fantasy stories.