The new series Fear the Walking Dead premiered tonight, and I'm wondering if Robert Kirkman, the other producers, etc, have discussed to what degree it can be considered canonical.
While I've never seen any of the people involved specifically use the term "canon" to describe the relationship, Robert Kirkman and Dave Erickson have made a number of comments indicating that the show is firmly within the same universe as the main show.
At SXSW, Kirkman said
"We're going to be focusing a little bit earlier," Kirkman said. "There will be hints and moments in the second show that if you go back and watch the first season of The Walking Dead will inform some of the discoveries that they had. It's going to be cool. We are trying to form an overall tapestry of a TV universe."
He has also mentioned to EW that the show will specifically line up with the main story.
“I will say that it will definitely progress,” Kirkman says, referring both to the outbreak and the story that accompanies it. “I will say that I don’t consider this show to be a prequel to The Walking Dead, because there will be a point where a certain episode of this show will line up with season 2 of The Walking Dead, and a certain episode of this show will line up with season 3 of The Walking Dead.
The showrunner Dave Erickson has said that everything done within the new show has been approved by Kirkman, and that certain storylines and plot points are specifically forbidden.
Just as in Kirkman's comics — which also won't ever reveal what caused the world as we know it to crumble — neither Fear nor the flagship drama will ever explain what happened to civilization. Erickson, despite his best pitches to Kirkman to touch on the subject, was shot down. "I had a couple of early pitches that touched on that and Robert shut me down. For him, it's never been about what caused it; it's always been about the impact it has on people," Erickson says.
"We won't see the CDC," Erickson says. "When we have two narratives living under the same umbrella mythology, the instinct would be to bring those two stories together and to conflate them. From a creative standpoint, I think we have enough story that we'll be able to ride on for quite some time."
Given how interwoven the two stories are, and the level of approval granted by Kirkman, it is reasonably safe to say that Fear The Walking Dead should be considered canon (or at least the same level of canon as the main TV show).
Despite earlier chatter that the two shows would not crossover, it was recently announced that season four of Fear The Walking Dead would indeed crossover by way of Morgan Jones (Lennie James) of The Walking Dead showing up. This explicitly confirms that the two shows exist in the same universe.