It was enough for me to give the episode a 10. As to the copyright, I'm not sure how an offhand mention is handled since they appeared in an episode before. I guess it would depend on Niven's contract back then and when he used them in a Star Trek comic strip.
No, it's the right franchise. The Kzinti showed up in the TAS episode "The Slaver Weapon". I assume you know this but making the reference for those that are confused.
I would like to know this as well. I know I spoke to Larry Niven about this 7 or 8 years ago, but all I remember is he was unhappy when they had Alan Dean Foster novelize this episode as he felt like he was competing with his own story.
Do you have a source for this? I can't find anything and the latest Baen Books Man-Kzin Wars anthology released a year ago only says "Copyright 2019 by Larry Niven".
The episode they appeared in originally mentioned 4 previous wars with Earth, there used to be a bunch of fan articles about how to try to reconcile that with Trek history.
My favorite reference of the series so far, loved it. For the record, I think Kzin may have been shown in a star chart on stream during TNG? But to actually hear it said out loud, and even pronounced correctly, that was pretty awesome.