I said "open source model" rather than just open source. While open source is only about the licence, I think publishing on GitHub typically implies a further model of accepting contributions, developing in the open, and being a part of that ecosystem.

In my experience this is how open source projects tend to thrive in the last 15 years or so. Projects that are open source but don't accept contributions and just dump a zip on a website somewhere once a year are a very different thing and lose some of the benefits.