It wasn't, but Linux was referenced specifically both in the article, it's title and another comment in here. My point was ffmpeg et al are available on other *nixes and even Windows too (I don't even mean Cygwin - they've been ported to vanilla Windows). So these are just command line tools - completely platform agnostic. There's no need for Linux to be singled out.
I know I'm nitpicking, but sometimes I feel there's an unfair bias towards Linux when people discuss open source software or the command line. And considering some of the aforementioned runs natively on Windows too, it's not even like we're talking about POSIX specific tools.
But in this case, I think it's OK. I read the article as being of the sort, "If you're using Linux, and need to manipulate media, here's the command line programs you can use."
I think most people who are familiar with the command line on say, OS X, can easily figure out that these are available there as well.
