So Tristi - you say an LDS author is a person who writes books and is a member of the church - what are you then if you are NOT a member of the church (or are considered an inactive member for many years) but you write a book that per your definition qualifies as LDS fiction? I'm curious because I'm doing exactly that. I was a convert and only went to church for two years before I left. I have nothing against the church, but I don't believe in it. My current novel, however, is definitely an LDS novel, about a girl who has struggled with her spirituality, left the church, and who comes to realize through her father's declining health and eventual death that she needs to return to the church. I wonder how I would ever publish such a thing, because I don't consider myself LDS. Sort of an odd quandry, no?
As far as I know, there's no rule that says you have to be LDS in order to write and publish an LDS fiction novel. It's an interesting question because I've never met someone who wasn't LDS who wanted to write for the market, but there's certainly nothing wrong with it. If your book was basically clean and kept with the genre requirements for LDS fiction, then I would say, it's LDS fiction.
If you did want to include some swearing or other elements that took it out of the LDS fiction genre, you could publish it as general fiction and it would be about LDS people, although not necessarily to be considered LDS fiction. You could publish that on the national market, which isn't entirely opposed to publishing stories about Mormons.
To verify what I'm saying, you might consider popping an e-mail to the various LDS publishers and ask them what their requirements are concerning Church membership for publication. I'd be really surprised if they'd turn down a book based on your membership or lack thereof (have you had your name removed from the records, or did you just stop attending?) but let me know what they say. I'll be curious to find out.
And thanks for the thought-provoking question!