I'm currently developing a website that allows users to record voice notes and upload audio files and then share them to Twitter. I'm currently using the MP3 format, but it is patented. I wanted to use OGG but it has a really low compatibility, so I want to know more about MP3 licensing. I'm currently hosted in the United States.
Is it legal to share the audio content that users record/upload in the MP3 format?
I see that Tumblr allows users to upload MP3 files and also distributes them in MP3.
Twitter also uses MP3 in TweetDeck.
But I can't see them in the Licensed Companies in mp3licensing.com
Assuming there's no problem with the copyright of the content inside the MP3 (artists songs, etc) that users upload, is it legal to distribute the content in MP3 format?
Also, according to Wikipedia, all the MP3 patents expired in the European Union. Does that mean that it's not illegal there, and if it's illegal in the US I can host the files there just to avoid legal consequences?