Why should people give their hard work away free ? I agree that open source is good for us but it's not good for the developer. With the rise of mobile tech, old style games are all the rage now. We could see many Amiga ,atari,msx , Apple2 style titles coming around again on iOS or android.
Look at organ trail for instance or flappy bird.
Serious programs or apps is different , amiga os productivity software is pretty much unsellable now although a few try.
Open source is great but don't expect much , 25 year old software has a habit of getting lost or damaged two.