Socialism

I'd also add that a fundamental difference between a worker co-op, and a foss-produced software, is that the code and often the output of that code (the app or library), are freely available, and anyone can use them and change them.

That differs from the isolated structure of a worker co-op, where production is isolated to a single firm and closed, the output is a commodity, and the goal is still private profit within the marketplace.

A good analogy would be that a worker co-op restaurant might keep its recipes private, in order to better compete in the marketplace, and increase it's own profit. A foss restaurant publicizes their recipes so that anyone can use them and improve them.

So while the production of foss might seem like a worker co-op, it's public nature and incentive structure imo makes it more akin to public ownership. There are a good number of cases of projects being forked, because the creators take the project in a direction the majority of it's users disagree with (libreoffice, hedgedoc, mariadb).

IMO We can only truly call it full public ownership, when states employ people to work on foss, and decisions are fully made at the public level.