Comment by amazari
Indeed, their work on WebKit, Servo, Mesa drivers, the kernel, and more is seriously impressive!
Their customers, Valve, in this case, deserve credit for being good FLOSS citizens (even if they are building a DRM walled garden on top of it :/), but the actual workers are the real unsung heroes. Them, Codethink, Collabora, and other open-source consultancies I might have missed are doing the community a huge service."
You can ship DRM-free games on it just fine. It's up to the dev/publisher.
Additionally you can get a lot of the benefits of Steam (Proton etc.) even for titles you didn't acquire through Steam - you can add and launch third party executables through the Steam client.
Steam is not exactly a walled garden save for some rather light curation of their own store.