You've got people (and companies) who are essentially making a deal with the community: "I wrote this because it was useful to me. Maybe it'll be useful to you too. If I share the code with you and you contribute a change back, we'll both benefit."
You've got the ones who do it for marketing reasons. Either companies trying to sell "Enterprise Edition" or support/hosting services, or developers trying to build their personal brand to get hired.
You've got products that begrudgingly throw tarballs over the wall to satisfy licensing obligations, like the Nintendo Switch web browser and most of opensource.apple.com.
...And then there's this guy, who is seeking rent on a linter configuration file.