The guideline is:

5.2.2 Third-Party Sites/Services: If your app uses, accesses, monetizes access to, or displays content from a third-party service, ensure that you are specifically permitted to do so under the service’s terms of use. Authorization must be provided upon request.

So, reading from the above, if Apple thinks you are doing the dodgy then they may request specific authorization proof from you which shows that the third party is ok with what you are doing. If you can't provide it, then they will likely not approve your app submission.