This is one of those questions where, if I was in the US I would ask you to seek legal advice. A nice thing about open source is that you can talk to the software foundations that define these licenses and ask questions (they all have a mandate to support or foster open source). You may still wish to talk to a legal rep of course.
There is a bit of a difference between extending or customizing Tomcat with additional functionality (you cannot use GPL code for this) and using it for its intended purpose of of running a web archive (which can be any license). If you want to include both in a “product” your installer can take care of the details - install tomcat (or ask your user to) and then install geoserver.war into the correct webapps directory.
Aside: GeoServer works with Tomcat by use of the Java Enterprise Edition APIs (such as “Servlet” distributed as GPL+CP). The “CP” defines a class path exception allowing Java to make use code that loaded in through a class loader. This is similar to the language in LGPL (where code that was compiled elsewhere is connected up via a C linker).
For this Servlet interface we have two projects playing this game. Apache Tomcat (implementing a server that makes use of this API to talk to web applications) and GeoServer (implementing a web application and trusting an application server will be around to answer HTTP requests and lifecycle control).
The exception you cite was made for the GeoTools library extends Eclipse Modelling Framework base classes distributed under an EPL license. GeoServer would not compile without the use of these classes. Both Apache Tomcat and GeoServer can be compiled without each other.
If you are really concerned about Tomcat you can do what we did for GeoServer - making use of a smaller application server called Jetty.
I was interested in introducing GeoServer into one of my product lines as
an additional feature; however, the GPL license limits me from doing so.
Furthermore, the suggested Apache Tomcat servlet container by the GeoServer
community forbids this as well due to the GPL license. I see there have
been some exceptions made for Eclipse. Am I missing something here?
I was going to include the GeoServer source code and licensing. My product
would not need to be linked to or combined with GeoServer; however, I would
prefer to distribute it with Apache Tomcat server. Please assist me if I am
mistaken in some way.
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