Usually when people say this they are referring to either Gitlab or Gitea. Well, it's not like all of Gitlab is fully open source, it's just Open Core, but I'm sure that's a sizable amount of the code, but I would imagine there's a decent chunk of gitlab.com source code that's proprietary (I'm sure somebody will quibble with this in a following comment, but the original argument is an argument of purism of being free and open).
Gitlab CE and Gitea doesn't solve the hosting issue, though of course Apache could probably pay somebody to manage that, but then you've introduced extra overhead for collaboration that most people aren't that inclined to solve.