NewPipe does not use any Google framework libraries, or the YouTube API. It only parses the website in order to gain the information it needs. Therefore this app can be used on devices without G-services installed. Also NewPipe does not store data on the YouTube website (no login), and it's free software.
Generally NewPipe is designed to not only support YouTube, but many more streaming services. However, right now NewPipe is not stable enough to support more than only YouTube. But if all works as planned, NewPipe will get such support by the version 2.0.