^You don't see a disagreement there? It sounds to me like it wasn't much of a secret.
I read an interview with ADF, IIRC, where he said he finally admitted publicly to being the ghostwriter, even though the original agreement with the publisher was that the story would not be revealed. "Splinter of the Mind's Eye" was essentially his compensation for not revealing himself as the author of the novelization.
So it was fan rumour for quite awhile, but eventually confirmed by ADF.
I'm kind of surprised they didn't add something about ADF on the covers of some of the newer versions, since it seems to be pretty much common knowledge that he wrote it, and not George Lucas. But I guess there would be legal issues that might cause problems.
Yes, I think ADF signed his contract knowing he would not ever receive a credit. And that's why he fought to get the original novel to be released about the same time.