At the heart of the Grokster decision is the idea that, if your business model is based on infringing copyright, you can be held liable for violations by third parties.
Most open source projects don't have a business model.
While it's likely that groups like the RIAA will want to pore over open source development records, looking for a "smoking gun" indicating someone thought about downloading Metallica with the resulting software, the fact is also that many open source projects aren't produced by companies, but by groups of individuals. With no money to take, a lawsuit for damages takes nothing.
In addition, the intent to violate copyright must be shown by the clear expression or other affirmative steps taken to foster infringement, according to Justice Souter's opinion. That's not a low hurdle. If open source developers keep their mouths shut all the RIAA can do is go after every user of the resulting software.
This means file trading will be going open source big-time. And I don't know how the industry can stop it. As former RIAA head Hilary Rosen (above) writes, "This volume needs to be embraced and managed because it cannot be vanquished. And a tone must be set that allows future innovation to stimulate negotiation and not just confrontation."
There's a clear way ahead to ending the copyright wars. There's also a clear way ahead toward escalating the conflict. Which way it goes is up to the industry.