I just bought app and keep getting error 304 whenever I want to download a video, any help? Is it iOS 7 comparable?

1. The latest version of MediaBurner is compatible with iOS 7.

2. 304 means the video is forbidden, there are many reasons that the YouTube doesn't allow you to watch the video, so I advise you to sign in to YouTube website and watch the video in building browser to see whether the video is open for you: just click top left "+" on the Channels tab and enter http://m.youtube.com and click GO to browse.