yup, though since they will require administrative permissions, I don't think valve will go around making you install it unless you play the specific game. Also I don't really understand how GPLv2 and kernel modules work, but I wonder if AntiCheats would be forced to open source themselves? Probably not honestly.
Edit: If anyone wanna read Linus's thoughts on it [1]. TL;DR It's a legal gray area.
This is a non-answer. Steam is not and should not be the sole source of video games on PC. This is a workaround that doesn't even work as well as you imply.
> Just use Windows. Install games from developers directly.
Proton (a fork of Wine) can be used outside Steam. It's open source and hosted on github. There are also forks of Proton that are community maintained (e.g.: Glorious eggroll).
If you want to have the convenience of Steam, without Steam, you have projects like Lutris, which have community maintained scripts for each game. Those scripts are responsible for installing all the necessary dependencies and workarounds necessary for getting a game to work.
You can check https://www.protondb.com/ to see which games work well under Proton. If you don't want to use Proton, you can search the Wine application database for compatibility information: https://appdb.winehq.org/
I recommend Steam + Proton because it's the most frictionless way of getting games to work. The #1 complaint about Linux is how hard it is to do some things (like the guy I initially replied to), but it doesn't have to be that way.
This can however change as Steam plans to use SteamOS (based on Arch) as their primary OS on the SteamDeck.