Re: GPL -- I think it's unfair to say GCC or Linux were a fluke. They've both received significant contributions because of the GPL -- like Objective C support, or any number of features in Linux -- and I expect that to continue. OTOH, I don't think the GPL is right for XMLObject. The GPL is difficult to use in a conglomeration of software, especially when the GPLed portion is small, and that's going to be the case with any library.
If I had a really awesome library, or some compelling reason to choose the GPL (e.g., business reasons, or I in turn used a GPLed library), then I might choose GPL for a library. I think there are very good arguments to be made for the GPL. However, in most cases it's not really right for a library. OTOH, I think it's perfectly fine for applications, and would be my license of choice in those cases.