The CD version does require Steam either for patches or to download the entire game but nothing more, once the game/patch is downloaded you can uninstall Steam and never have to use it nor will you have to be online again to play. The reason for this is because larian are working on the game and making massive additions to the game that couldn't be ready in time before the discs went in to be manufactured. Beyond the one time download the game is very much DRM free.
You also do not have to use the disc/Steam to download and install the game. On you Larian Vault pledge management page you can select whatever platform you want the game on and you'll get a key for that so if you want to create additional accounts you can just select a Vault version of the game but GOG(who are also amazing guys and a great DRM free platform) is also an option.
