The phenomenon of TV copying each other is well known. Last year there were two Beauty & the Beast shows in contention. Serial killers seem to be the big thing this year. For next season, there are two shows where the gimmick is that Dracula, Frankenstein et al are in the same story.
If only there were so many space operas bumping heads that they were copying each other or seeming to. Why should I care if some show steals from another? That's for the lawyers to sort out. If they got a case, go for it. The fact that nobody is suing right now is proof that there's not enough of a case to interest a lawyer because in California, there are so many lawyers per capita that they'll jump on any vaguely viable case like hungry hyenas.