Cheat Engine contains GPL-licensed code but disallows commercial use
Let me clear up a huge and very common misconception: an (alleged) GPL violation like this doesn't mean that you, the recipient, suddenly has the right to demand that the rest of the code be released as GPL. All it does is give the copyright holder of the GPL'd code a legal claim against the developer of the infringing product. It's unlikely that even the copyright holder could get a court to award anything but monetary damages. Courts are very reluctant to order specific performance (i.e. release all of your code as GPL) of a contract instead of just granting monetary damages. (Like a reply points out, the copyright holder is likely to win an injunction against further infringement.)Importantly, the new code in the infringing product is still copyrighted, and that copyright is owned by the person who wrote that code even though they also violated the GPL license of other code.Edit: Good point about the SFC/Vizio case. I would be surprised if the SFC wins, but it's a clever argument. It would be a major earthquake for the free software world, but maybe not an earthquake in their favor. No one is going to touch GPL code with a ten foot pole if it gives the entire public standing to sue you.