FFMPEG. Look at the amount of legal horse fertilizer here: https://www.ffmpeg.org/legal.html ... and every time I've seen people asking what they can and can't do, someone from the ffmpeg devs (once in a couple of years when they actually respond to someone) just says "talk to your lawyer". I mean, flip a few switches and suddenly you're under a different licence ... and all this you have to look up yourself. Many (especially smaller) devs just don't care and distribute ffmpeg together with their (often non-oss) tools. Given the amount of these in the wild, if someone really had an axe to grind, they could sue hundreds, maybe thousands of devs of all sizes. It's a total minefield. And one of the most popular (L)GPL packages in existence.