(written from a Production point of view)
Laurence van Cott Niven (born 30 April 1938; age 79) is an American science fiction writer who wrote the Animated Series episode "The Slaver Weapon" and co-authored the Star Trek comic strip story arc "The Wristwatch Plantation". Niven is best known as the creator of the Known Space universe, for which he has written many novels and short stories. Ringworld is the most famous of these novels, winning the 1970 Hugo and Nebula Awards awards.
Niven became involved in writing for The Animated Series upon the request of Dorothy Fontana. Being determined to make use of animation, his first draft included the mysterious Outsiders from his Known Space universe. This idea was dropped because it was too science heavy and as such not suited for a Saturday morning cartoon show. It later became the short story "The Borderland of Sol", set in the Known Space universe, and won a Hugo Award for Best Novelette in 1976.
The same problem of inappropriate subject matter applied to Niven's second pitch, which Niven himself described as too bloody.
When Fontana and Niven met with Roddenberry at his place, Roddenberry suggested that the short story "The Soft Weapon", which Niven had published in the Known Space short story collection Neutron Star, should be re-written to become an episode of animated Trek, and Niven agreed. Thus, many elements of the episode, renamed "The Slaver Weapon", including the Kzinti race, stasis boxes, and the slaver weapon itself, were adapted from the Known Space universe. Gene allowed Niven to leave out Kirk and only use Spock, Sulu, and Uhura to replace the main characters of his short story.
Paramount later sold novelization rights to Ballantine Books and "The Slaver Weapons" was novelized in Star Trek Log 10 by Alan Dean Foster. Niven, as a novelist, effectively wound up competing with himself. He was unhappy with this, though, contrary to popular belief, no legal action was ever threatened or taken. 
In 1981 Niven was again asked to contribute to the Star Trek universe when he was asked by Sharman DiVono to work on a comic script. Together with her he wrote a comic story that was drawn by Ron Harris, produced by the Los Angeles Times and published in the Houston Chronicle from 1 March 1982 to 17 July 1982. The two authors considered publishing the story later as a novel and had already received permission from the authorities at Paramount Pictures and the Los Angeles Times. However later the authorization from Paramount was withdrawn when the chief of merchandise was replaced.
He also worked with Steven Barnes on a number of novels, and Barnes later went on to author one Star Trek novel, and a short story.