This. I suppose you could argue it's also a source of enormous human frustration and negative impact, but fundamentally Linux changed how software worked as a whole. Server operating systems quit being a business, which commoditized the concept of owning a server to it's logical extreme. It ushered in a panoply of suitable software replacements for expensive things like C compilers and web servers, which would eventually whither away as viable products entirely.
At the expense of killing a few exploitative businesses, Linux created a better world for millions of programmers and the hundreds of millions of users that rely on the web staying free. It's hard to imagine an alternate reality where Linux doesn't exist but the internet does - we'd be relying on the BSD-likes to not get forked into commercial systems, which is a pretty unstable premise.
