You need to make sure you know the licensing of all of the content in an App that you don't produce yourself. Just because something is "a public video" doesn't

You need to make sure you know the licensing of all of the content in an App that you don't produce yourself. Just because something is "a public video" doesn't mean you can use it. Putting it in an App will likely count as copyright infringement, and you are liable for damages. They could ask Apple to remove your App, and the could also ask for $10 for each time someone downloaded the app that included their content. In the US, the author (or artist) owns the copyright to all content they create unless they specifically state otherwise. Even most "free" content on the web has a clause that you must credit the source, so you can be liable for infringement of creative commons content that would otherwise be ok to use without payment. An App, even a free one, would probably be considered commercial use, so the content available to you is smaller, and the penalties for use are larger. You should be careful. I am not a lawyer, and you probably don't need to talk to one every time you need to go looking for content for an App, but you should be sure that all of the resources you use are licensed correctly.