>> If Tomcat were under GPL, we wouldn't be using
>> Tomcat.  Simple as that.
>
> You most likely would, since you are insulated from the tomcat
> implementation by the servlet/jsp/jsf/whatver interface specification.

Corporate lawyers don't want to even here the word GPL, much less
debate what makes something a derivative work.

In a company large enough to have its own lawyers, just mention the
word GPL related to one of your software releases and see what happens
:)