He didn't give it away. He licensed it under a specific license he chose and people have to accept if they want to use his work. Say that I help you with some

He didn't give it away. He licensed it under a specific license he chose and people have to accept if they want to use his work. Say that I help you with some endeavour of yours, and that I do that provided you do the same with an endeavour of mine. You accept, so I help you, then you decide to not help me. The harm is that you have extracted value from me by promising to me something you didn't deliver. In the GPL licensing case, the harm is that he choose to provide his code under GPL provided those who use it would put changes and derivative works under GPL too. In particular, this means that VMWare choose to use GPL code knowingly they would have to share the result but they didn't. The harm is much bigger in that everybody who is happy with GPL code can't use VMWare's code. That's a lot of people.