WebM is 100% free, and open-sourced under a BSD-style license.
https://www.webmproject.org/about/ libvpx -> https://github.com/webmproject/libvpx/blob/master/LICENSEThe libvorbis reference implementation provides both a standard encoder and decoder under a BSD license.
https://xiph.org/vorbis/ Todo libre \o/
