I picked up IDW Publishing's latest comic, "Assignment: Earth" #1 by John Byrne, last night and it looks great. Read it on the train home. Some fun 60s stuff; at times "Brighter Than a Thousand Suns" felt like it had been made in the 60s, although I'm so glad the paper quality was better! I assume Teri Garr had to sign off on her likeness? (I still remember her "Starlog" interview; possibly the only ST guest who doesn't have fond memories of her association with Star Trek and its fans - not that ST actors have to have fond memories, but her interview was quite... angry and bizarre when the topic turned to ST, IIRC).
Contracts of the 80s and 90s (and beyond) have very different wording to those of the 60s. Recently it was mentioned here that the original cover of the forthcoming Kevin Ryan "Errand of Fury" novel, from Pocket Books, was to have featured the TOS Organians, but that there was no permission for one of the deceased actors so the cover would be changing.
DC Comics had to draw a bald Garth of Izar, a ST III Captain Styles with no mustache, and a fat guy who vaguely-resembled Harry Mudd's physique for various issues. (Due mainly to existing likeness permissions not being on record.) When DC wanted to bring back Saavik in Series II, she had to resemble Robin Curtis, not Kirstie Alley, even though Kirstie's Saavik was more popular. And so on.
Sometimes the families of deceased ST guests might be happy to sign off. Others might insist on a royalty. Others might want approval of finished sketches, or they might refuse outright. It may vary from actor to actor, too, depending on their (and their agents') clout when contracts were signed. Welcome to Hollywood: a land of red tape.