Libav Adds OpenH264 Encoder Support: Good Performance, BSD Licensed
The OpenH264 encoder support was added to Libav's libavcodec since it's BSD licensed rather than GNU GPL, the performance and quality is comparable to x264, and it's simpler to hookup. This OpenH264 Libav support requires OpenH264 v1.3 or newer.
OpenH264 can't be shipped though as part of Libav but must be downloaded at runtime on the end-user system. Per the commit message by Martin Storsjö who added the support to Libav, "To take advantage of the OpenH264 patent offer, the OpenH264 library must not be redistributed, but downloaded at runtime at the end-user's system."
OpenH264 is the open-source H.264 video codec released by Cisco in 2013 under the sumplified BSD license that they've made available free to the open-source community. OpenH264 is currently in use by Firefox and other open-source applications.