Datasheet

Chapter 1
6
Distributing Tomcat
Tomcat is open source software, and as such is free and freely distributable. However, if you have much
experience in dealing with open source software, you're probably aware that the terms of distribution
can vary from project to project.
Most open source software is released with an accompanying license that states what may and may not
be done to the software. There are at least forty different open source licenses out there, each of which
has slightly different terms.
Providing a primer on all of the various open source licenses is beyond the scope of this chapter, but the
license governing Tomcat will be discussed here and compared with a few of the more popular open
source licenses.
Tomcat is distributed under the Apache License, which can be read from the
$CATALINA_HOME/LICENSE file. The key points of this license state that:
❑ The Apache License must be included with any redistributions of Tomcat's sourcecode
or binaries
❑ Any documentation included with a redistribution must give a nod to the ASF
❑ Products derived from the Tomcat sourcecode can't use the terms "Tomcat", "The Jakarta
Project", "Apache", or "Apache Software Foundation" to endorse or promote their software
without prior written permission from the ASF
❑ Tomcat has no warranty of any kind
However, through omission, the license contains these additional implicit permissions:
❑ Tomcat can be used by any entity, commercial or non-commercial, for free without limitation
❑ Those who make modifications to Tomcat and distribute their modified version do not have to
include the sourcecode of their modifications
❑ Those who make modifications to Tomcat do not have to donate their modifications back to
the ASF
Thus, you're free to deploy Tomcat in your company in any way you see fit. It can be your
production web server or your test servlet container used by your developers. You can also
redistribute Tomcat with any commercial application that you may be selling, provided that you
include the license and give credit to the ASF. You can even use the Tomcat sourcecode as the
foundation for your own commercial product
Comparison with Other Licenses
Among the previously mentioned rather large group of other open source licenses, there are two
licenses which are particularly popular at the present time: the GNU General Public License (GPL) and
the GNU Lesser General Public License (LGPL). Let's take a look at how each of these licenses compare
to the Apache License.