Does "tipping" have to go through in-app payments / in-app purchase?

I have an app where content will be available for free. However, if someone appreciates the content, they can send a monetary tip to the content author as a "thanks." The money they send will travel through my org, which MAY take a % cut to fund operations, and then be passed along to the creator.

Does this workflow require use of in-app purchases? If not required, can I use in-app payments? I've read the rules and this flow isn't specifically addressed.

Thanks in advance for any help!!