This fork was launched over the weekend and was already brought up in our forums. Though as this change has just been announced hours ago, it's not yet clear which developers are behind this change and the other details involved.
All of the FFmpeg assets are being transferred to libav.org. As some readers have already expressed, the new libav name is also arguably confusing with there already being the libva project (VA-API lirary), libavcodec (the A/V codec library as part of FFmpeg), etc.
More details as they emerge.