Contributing to open source is not contributing to free software, the big 5 are indeed all doing quite the opposite: creating walled gardens, trying to monopolize the distribution of software and goods, and pushing for a web monoculture.
Also, they are making the web a more centralist and frankly, boring, place.
"creating walled gardens, trying to monopolize the distribution of software and goods, and pushing for a web monoculture"
...and spying on users.
…that's a strange choice. Basically every company in that comic contributes in some way to open source.