If you violate the GPL, you have violated the GPL, that's it. Your code does not become GPL automatically. Even many OSS advocates sadly get this wrong.
Perhaps Syke meant it differently, but it's important to fight the "viral" FUD.
I would say with items like Chrome taking a majority of the browser marketshare and cups being the defacto printing system of choice for non-windows machines there are a lot that would disagree.Now I can't say there are no contributions, I'll have to say there are no significant contributions ;-)
Everything present in the the Mac OS implementation is present in the release that you enjoy in your distribution. Fact is that Apple after purchasing CUPS could have just as easily changed the license leaving the opensource community with an older version of CUPS to base a forked version on. This has not happened however and CUPS continues to be maintained and developed in a open manner.Apple didn't invent CUPS, they instead slowly pushed their changes upstream and when they got tired of it they purchased CUPS and re-licensed it they could continue on their proprietary way without having to contribute everything back.