There are a few things that I don't understand about this thread, or rather, about some reactions.
No one is forcing anyone to share their code against their will. It is always the author's (or... current copyright owner) decision whether to open their code or not. And I think it would be wrong to try to somehow "force" the source release on the author.
Sure, I think it would be better if more Amiga projects would be open source, or at least... more open in their nature (since it's so helpful for others in the community!). But it's just an opinion. And on the internet, you know, everyone is entitled to have an opinion. Me having an opinion does not necessarily mean, I expect everyone will suddenly comply with my vision of the world.
Dear developers. If you are hesitant, how about trying to build your next Amiga project in open source way? As an experiment. Give it a try. Maybe you'll see the advantages of this way once you try it. It's fun collaborating with others. It's also an excuse to push yourself further. Write better (or more readable) code, help others understand it. Etc.