It's not censorship because people still have access to it. The supreme court has already held it's okay to put small reasonable restrictions on certain types of speech so long as you don't forbid it altogether. Putting a small fee on obscenity to prevent access by minors and fund human trafficking is well within the bounds of the first amendment.
Free speech is not some pure beautiful ideal concept. It exists solely as a creation of the constitution as interpreted by the Supreme court. And there is strong precedent from the Supreme court that these types of restrictions are perfectly compatible with the first amendment.