What source are you getting this from? Not saying I don’t believe you, but I find that really strange since, as
@mtpelepele pointed out, Volcano was made by 20th Century Fox, not Paramount. Searching through Wikipedia and IMDB, I can’t find any reference to Paramount being part of the movie or owning/buying any rights to it.
Plus, the film takes place in Los Angeles and is about a mysterious volcano that suddenly forms within the city — completely unrelated to the theme of KD’s Volcano, which was themed to an expedition of a huge volcanic mountain in some tribal region of Africa. So, it’s not like KD’s Volcano borrowed any elements from the film’s story or setting at all. It seems to me that the film and the ride were totally unrelated and just happened to share the same name. Why would KD need to purchase the rights to use the generic word “volcano”?