Maybe you should point out some open source success stories. Yahoo is built on open source tools. So is Amazon. eToys was mod_perl and Linux (the business model failed, not the technology). Ticketmaster and CitySearch are heavy open source users, and so is Morgan Stanley. There are many more examples like this. The important thing is to understand that using open source tools (and contributing to their development) does not mean you have to make all (or any) of your company's IP public.