"It is fair to say the GPL does not intend to make it easy for proprietary software.The intention is to liberate code and ensure continual downstream benefits to users. So, yes, it's going to be easier to integrate open source code into a GPL'ed environment. And, as it should be!
It is important that community environments also ensure that open source developers benefit more than proprietary developers. It hasn't been that way in J! [Joomla!] or in Mambo."
--Amy Stephen, OpenSourceCommunity.org, Comment to CMS Report's Is bridging a GPL application with a non-GPL application legal?