I’m trying to understand, since it’s DRM-free, can I buy it and share with many people so they can play it on their PC? Or there’s something that prevent me to do that?
Does it mean that pirating GOG games is easy as transferring to other machine?
If so, I wonder why pirate sites like FitGirl still use cracked Steam version of games, why don’t just share GOG version?
Pretty much. It would violate copyright etc, so still illegal to share (as far as I know, I’m no expert). Sites do exist for gog cracked games. FitGirl etc take from steam, as not all games are on gog. But there are dedicated sites for gog piracy.