Thanks @Thorfinn, I wasn't aware of the generous refund policy! And while I'm generally on your side regarding your suggestions, it just wouldn't be appropriate.
You see, if I were to buy the game for the others I would more or less compel them to play the game for at least a few hours (and if I would start with one family pack, I'd split up the group). Therefore they'd most likely reject this offer right away - even if we could refund the accounts afterwards. I will definitely show it to the guys on my PC and who knows, maybe one or two will buy it afterwards and we'll play together remotely after the LAN party.
But my main point was that I wish that Vintage Story had a less strict "authentication policy". I've only heard about it in a "Most Overlooked Survival Games"-kind of YouTube video, which I think is a shame. As already mentioned by others in this post there are examples of indie games that sell extremely well despite being easy to play without a purchase. And I want to add Beyond All Reason to this list. It is an excellent, completely free indie RTS game, which is financed only by donations. You can even host matches on their servers for free.
Not saying that Vintage Story should be free as well, but I doubt that strict piracy protection is really suitable for indie games. Indie games should be as accessible as possible to compensate for the lack of large marketing campaigns.
But as @LJim said:
