jd writes "There are many pieces of software out there, such as seL4 (kindly brought to my attention by another reader), where the vendor has indeed engineered something that they're entitled to Close Source, but where their closed-source license includes the modifications to GPLed software such as the Linux kernel. Then there's a second type of behavior. Code Sourcery produced two versions of their VSIPL++ image processing library — one closed-source, one GPLed. It was extremely decent of them. When Mentor Graphics bought Code Sourcery, they continued developing the closed-course one and discontinued, then deleted, the GPL variant. It's unclear to me if that's kosher, as the closed variant must contain code that had been GPLed at one point. Here's the problem: complaining too much will mean we get code now that maybe four or five people, tops, will actually care about. It will also make corporations leery of any other such work in future, where that work will be of greater value to a greater number of people. So, the question I want to ask is this: When is it a good time to complain? By what rule-of-thumb might you decide that one violation is worth cracking down on, and another should be let go to help encourage work we're never going to do ourselves?"