Depends. Steam is not DRM itself, you can open the game folder and copy the game to another computer and steam doesn’t care. The game often has its own DRM though which will stop you.
GOG is different in that they ban DRM outright.
> The game often has its own DRM though which will stop you
I think you missed the "know where to look" part. It's called a Steam emulator, for starters. Note that I speak about this strictly for preservation purposes, as people who raise Steam DRM as an obstacle to preservation have not done their homework.
Some games won't start if Steam isn't running but you can work around that with a fake steamapi.dll, it's not a deep DRM check.