The point people keep talking about here as risky are: what is a derivative work, and what constitutes complete and complete corresponding source definition. Both of those things HAVE been tested. complete corresponding source definition is the same in gplv3, almost exactly the same in gplv2. Derivative work is a general copyright thing tested in many cases. The extra paragraph doesn't have anything to do with them. To recap: 99% of the license is tested, and the "risk" everyone is discussing are about the parts that have already been tested. Basically, what Drew wrote is true.