I've met people who thought DRM-free meant shareable. It's not the case.
DRM-free just means there are no technological things in place to keep you from making copies. DRM-free means that you can play your game without having to be connected to the internet, or pull out your magic word-finder, or get a glitch that eats your saves because it thinks you stole it.
By the TOS at the store, you can share your games only amongst your household.
An old article that I'm sute I won't find right now had a rep for GOG saying that you could treat yourbgame like a CD. You could loan it to a friend if you weren't playing it. That is against the TOS, but I don't think GOG will be upset if your friend D lent you some games that he's no longer playing to try out. Bit if you like the games, I'd recommend buying them.
Buying games puts mkney into game maker's hands. Those few extra bucks you talked about above are very important to developers. Many developers work for very little money. Some only make money after years and years of fee work (bioware doctors didn't take a dime for 5 years according to an interview I recently read in game informer). And those dollars deed their family. They also keep studios making new games. Lots of studios close when people don't buy their games.
As for your answer, GOG Galaxy is a non-required client. To purchase games on gog that work with your account, you can either purchase them, get them from a gift code, or get freebies during promos. Neverwinter nights was just given away, for instance.
I think most people here have prorated a game before for many reasons. But when a storefront makes a massive move to help people enjoy their classic games anf new games while trusting their customers by removing their DRM, Then it would be an appropriate response by people who are thankful for that decision to honor it through thoughtful purchases and diligently avoiding piracy.
Lastly, it is wrong. I don't think you care much about right and wrong for some reason, but enough people doing a wrong thing can really screw someone over. So I would applaud you if we're to do the right thing here. Try out the games, buy what you like.