GOG has always been big on non-DRM and giving you direct access to the installers. They do have a launcher, which likely has similar terms as Steam, but there’s no way to enforce the way people use installers.

So it’s more similar to physical media–there’s still legislation, but I don’t believe “passing on” a game would be any more illegal than passing on a physical disk.

And GOG has always been in favor of this model, to my knowledge.