For us, consumers, yes, MP3 has and will continue to be free to use. However, the MP3 wasn't free for anyone to use. To be able to listen to MP3 files, you had to have a program that could play them. Fraunhofer had patented the encoding and decoding algorithms, so any software that wanted to support MP3 formats had to pay Fraunhofer a license fee.
This wikiHow teaches you how to download the music you want to put on your MP3 player for free. In addition to free music tracks, YouTube's audio library also includes sound effects. Once again, they're free to use in all your creative work.