My DAW is very rarely online and adding most VSTs isn't a problem. Some plugins, especially virtual instruments, require online activation. But it's really up to the 3rd party what the activation rules are for their plugins. So some companies require a license and you can get it online - on another machine and copy it over, some don't have any DRM, and others require online actiation. You'd have to check with the manufacturer of the plugins, S1 doesn't care, the plugin manager will read your plugins whether you are online or not, they just might not work depending of the manufacturer... I've never had a problem with an activated plugin not working because I was offline.