So I got the e-mail with the download links 1 for windows and mac ect… when I give the windows link to my friends they can also download the game without buying it as well? Is this normal or meant to be like this?
There is a measure of trust in you not to just give it to your friends. If you wish to show support to greenheart, you could recommend your friends buy it, it’s not overly expensive 
The EULA state : maximum 3 computer with the game.
There is no check of that, but