Folks may recall that we at Star Trek Phase II had started pre-production on Jimmy Diggs' Kzinti script--adapted to a Kirk-era story. We were stymied by not being able to secure the production rights to the Kzinti from the gentleman to whom Larry Niven sold them years ago. We started to forge ahead with the felinoid race being called the "Kytheri." Ultimately, there were just too many obstacles to overcome and we had to backburner (way backburner) to episode.
Forgive me, but I find that a bit paradoxical, considering that technically you don't have the rights to shoot productions based on Star Trek
in the first place. It's tolerated as long as you don't try to make a profit from it, but it's not actually authorized or licensed. So why would lack of rights be an impediment where the Kzinti are concerned but not where Star Trek