Although the novel Peter Pan (also known as Peter and Wendy) is in the public domain in the US, the play (and stage adaptations) is in copyright there until 2023.
This is because the novel was published in 1911, but the play itself was only published in 1928, so its copyright was extended by the new term of first date of publication plus 95 years (set by the Sonny Bono Copyright Extension Act of 1998 for works published between 1923 and 1977).