What happened was, DC waited until some rights expired before using Peter Pan. In the previous issues of Fables, they had specifically not included Peter Pan.

I quote now from commenters to issue 152: "when J.M. Barries (the original author of Peter Pan) died, he bequeathed his rights to a children's hospital in England. In reality, that would mean that he bequeathed them to England itself since the country manages the hospitals. In the 80s, when the copyright should have ceased, because of monetary issue, England voted a law which allowed the copyright on Peter Pan to exist til 2007"

https://readcomiconline.li/Comic/Fables/Issue-152 reader comments section at the end

What happened was, DC waited until some rights expired before using Peter Pan. In the previous issues of Fables, they had specifically not included Peter Pan.

I quote now from commenters to issue 151: "when J.M. Barries (the original author of Peter Pan) died, he bequeathed his rights to a children's hospital in England. In reality, that would mean that he bequeathed them to England itself since the country manages the hospitals. In the 80s, when the copyright should have ceased, because of monetary issue, England voted a law which allowed the copyright on Peter Pan to exist til 2007"

https://readcomiconline.li/Comic/Fables/Issue-152 reader comments section at the end