Think of an artist, a music producer, and a designer. Their artworks are protected by what's called 'copyright'. For the computer industry, copyright is at the center of software. Companies like Microsoft know much about it.
Then comes open source-related software. The codes are available freely to anyone and anyone may modify them to adapt to a new situation or free to use them.
Based on my ethics classes, I've always thought that any new creation is automatically protected by copyright, even if that's not stated. That's because most countries have signed the Berne Convention.
But for open-source software things weren't clear up to now: does the author retain copyright even if everyone's allowed to use and modify the codes?
Not now. This story from the BBC reports that a US federal court has made a ruling where the author retains copyright, and that all works based on the author's code should respect the license.
Such protection for the merit of the original works is a good thing and will encourage more of us to publish our work as open source. The fear of losing recognition will now fade away and authors of derivative works will be forced to properly acknowledge the original works.