What is the difference between ffmpeg and ffmbc now?
Usage differences

Note: ffmbc/ffmpeg will refer to the tools, while FFmbc/FFmpeg will refer to the projects themselves and/or each whole collection of tools and libraries.


There are syntax differences including:


ffmbc uses the old, confusing -newaudio option while ffmpeg can just use -map.
ffmbc does not support -codec or -c, so instead all stream types must be explicitly defined if you do not want to rely on the defaults. For example -vcodec copy -acodec copy -scodec copy vs just -c copy.
Probably lots more that I didn't think of. Feel free to edit answer and add more.

ffmbc will automatically relocate some data after encoding to MOV, MP4, etc while ffmpeg requires the -movflags +faststart option.
ffmbc does not support -filter_complex so filtering is different. For example, using the overlay video filter:


ffmbc: -i video.mp4 -vf "movie='overlay.png' [movie]; [in][movie] overlay [out]"
ffmpeg: -i video.mp4 -i image.png -filter_complex "[0:v][1:v]overlay"

FFmbc seems to support more broadcast formats.
FFmpeg has more features and filters.
FFmbc dropped ffplay and ffserver.


Development differences


FFmbc is GPL, and FFmpeg is mostly LGPL which makes porting features from FFmbc to FFmpeg more difficult.
FFmbc is basically the project of a former FFmpeg developer with a few contributions from others. FFmpeg has many developers and contributors.
FFmpeg often merges things form Libav, while FFmbc ignores Libav. Libav cherry-picks occasionally from FFmpeg, but ignores most stuff from FFmpeg (Libav is often joked to have "NIH syndrome").