UPDATE 7/31/2015 4:40 PM PT: "Spider-Gwen" writer Robbi Rodriguez has commented to Newsarama, saying in fact there is no rule against creating new characters for the series.
"There is no rule," Rodriguez told Newsarama. "The subject wasn't explained to me very well when I asked before at the time, but it's all cleared now when I asked again not too long ago. I forgot I mentioned that on the podcast, so I asked them to edit it to clear up any future confusion. I meant to do the earlier and its my mistake for not jumping quicker thus causing this misunderstanding."
While speaking with the Spider-Man-centric podcast "Superior Spider-Talk," "Spider-Gwen" artist and co-creator Robbi Rodriguez discussed one of the more interesting stipulations put in place for him and writer Jason Latour.
"We can't really create new characters in 'Spider-Gwen' because the movie rights aren't officially fully licensed by Marvel," said Rodriguez. "Whatever we create in 'Spider-Gwen,' Sony gets first crack at those characters. So that's why we start doing what we call 'sampling.' We'll sample ideas that we have and slap them on to a new character. Say, we have Luke Cage, which I think we are planning on using, it has to be Luke Cage in name only. He is a new idea that we've had, for a new character."
The podcast and article containing these quotes have since been pulled, but Bleeding Cool spotted them as well as a cache of the original piece.
The quote touches on something that fans have theorized for a while -- that movie rights impact how characters are created and used in the source material. These theories have centered around the X-Men in the past, as their movie rights are owned by Fox. Despite striking up a deal with Sony to bring Spider-Man into the big screen Marvel Cinematic Universe, Rodriguez's quote hints that Sony still could still have a bit of independence when it comes to the wall-crawler's movie rights.
It's worth pointing out that if accurate, the "no new characters" rule seems to only apply to "Spider-Gwen"; since the book is set in an alternate reality, characters like Frank Castle, Matt Murdock and Felicia Hardy have all popped up in the series with drastically different status quos than their main Marvel Comics counterparts. However, new characters have been introduced with regularity in Dan Slott's "Amazing Spider-Man," and the same is also true for the books in the "X-Men" line as well.
Comic Book Resources has reached out to Marvel for a comment.