Right, if you download the offline installers, then they can’t stop you from doing whatever you’re going to do with it but you don’t own them. Legally, you can’t sell them, transfer them to someone else, etc.
There are other sections that make the lack of ownership by you clear and that you still have to abide by the publisher’s/developer’s licensing agreements but Section 10 states the situation outright:
Section 10 of the GOG user agreement says:
GOG content is owned by its developers/publishers and licensed by us.