Correct. This is what makes me feel guilty about releasing a closed-source product, or even one with a non-OSI license. It’s irrational, but I feel like I’ve benefited so massively from FOSS that I owe it to the community to contribute back.

EDIT: as another commenter wrote below, OSI is driven by massive cloud vendors, who have a vested interest in having their freedoms to take projects and monetize them. Perhaps a somewhat restrictive license isn’t a bad thing.

Open source as a byproduct of a company absolutely works - it's been proven by tons of tech companies.

But if you open source your revenue-generating parts, and only charge for support/managed version/enterprisey features you'll end up with quite weird incentives, particularly with infrastructure tools, in which the big cloud providers will happily compete with you, using the version you open sourced and providing and ecosystem to their customers that one simply cannot compete with

In the sense that most modern programming languages and compilers are open-source, sure, nothing outside the embedded world can truly be built without relying on open source.

There are still native shops that rely on very little open source, though at this point probably only in niches like gamedev or defence.

They were possible for quite some time, I guess people born after Linus created Linux have no idea how we used to pay for everything, or pirate.

I would imagine there is a lot on Windows possibly macOS.

Many c/C++ libraries are not open source - even more .Net ones