The internet is a communication device, and we should be using to its max. All questions about distinguishing different kinds of copying, and whether one is moral or not, do not reach the real heart of the matter. All copying (assuming good stuff) is good, ultimately, and we ought to fit our commercial system to that, not the other way around.
This isn't true freedom. I am not allowed to copy open source software into my commercial application without releasing my revisions.
It's also funny that you mention open source, because it's eventually going to bring down the wages of developers. This is because the difficult parts (IE: the software that needs to be engineered) is given out for free and businesses only need the mechanics to make changes (lower education, skillm and pay requirements).
The problem is how do you make it possible for the best people making music (or whatever other internet good) to completely sustain themselves via things they put online.