libav was the hostile fork, not FFmpeg. Someone removed write permissions from key contributors (or contributor. I forget) and just about everyone sided with those contributors, thus the instigators were forced to rename their project. The development effort stayed on FFmpeg, even as the libav people tried porting back the changes. Eventually libav passed into irrelevance as it failed to acquire mindshare and distributions stopped including it.

It's been a while since I read the story but I believe it did prompt some changes in ffmpeg management, that's why I was saying it was a hostile fork success story.

glibc would be a better example in that case.

libav was the fork [1], and libav is dead now [2,3] (and many developers returned to ffmpeg).

libav was forced to rename their project because Fabrice Bellard, still owner of the trademark and the ffmpeg.org domain, did not hand it over. ffmpeg put in much effort retain compatibility with libav, mostly by merging all their changes wholesale, while libav ignored ffmpeg, including and most crucially, their security fixes [4].

[1] http://blog.pkh.me/p/13-the-ffmpeg-libav-situation.html

[2] https://www.libav.org/

[3] https://www.phoronix.com/news/FFmpeg-Back-In-Debian

[4] https://j00ru.vexillium.org/2014/01/ffmpeg-and-the-tale-of-a...