I’m not entirely familiar with the process, but I think Goldberg uses steam architecture, but replaces calls to steam servers with locally emulated ones. And I think Steamless emulates the DRM check locally, to spoof the call to steam servers. Neither tool requires internet or active steam servers to run. If the internet disappeared tomorrow, as long as I had my game library downloaded, and the latest version of those two tools installed, I could play all my games forever. Of course, I still prefer to buy my games as physical copies or offline installers from GoG, but you kinda have to go where the games are.