For a long time publishing source code under a freedom givinglicense was considered bad. What if people would take your code and reuse it? What if you don't like how they reuse it?
History has shown that this has happened in only rare cases. And even then, having your code reused is an homage towards your creation. People started to understand that and it gladly became very common practise.
But it seems like the story starts over from the very beginning again, the field though is a different one. It's now graphic artists and especially musicians who are facing the same fears this time. But I think, it shouldn't be me writing this because I'm neither (well, only very few people consider ASCII art as proper art. Probably even less than consider good code to be art..). Good thing is, I don't have to. One of the wesnoth graphic artists did it, and way better than I would ever be able to get the idea across. So here you go: Jetryl about GPL Policy in wesnoth. It might be long, but it's definitely worth the read, and I hope it will help to make some people understand better and fear less.