Datasheet

Apache and Jakarta Tomcat

GPL

The GNU Project created and actively evangelizes the GPL. The GNU Project is somewhat similar to

the ASF, with the exception that the GNU Project would like all of the non-free (that is, closed source or

proprietary) software in the world to become free; the ASF has no (stated) desire to do this and simply

wants to provide free software.

What Does It Mean to Be Free?

Free software can mean one of two entirely different things: software that doesn't cost anything, and

software that can be freely copied, distributed, and modified by anyone (thus the sourcecode is included

or available); such software can be distributed either for free or for a fee. A simpler way to explain the

difference between these two types of free is "free as in free beer" and "free as in free speech". The

GNU Project's goal is to create free software of the latter category. All uses of the phrase "free software"

in the remainder of this section will use this definition.

The differences between the Apache License and the GPL thus mirror the distinct philosophies of the

two organizations. Specifically, the GPL has these key differences from the Apache License:

❑ No non-free software may contain GPL-licensed products or use GPL-licensed sourcecode. If

non-free software is found to contain GPL-licensed binaries or code, it must remove such

elements or become free software itself.

❑ All modifications made to GPL-licensed products must be released as free software if the

modifications are also publicly released.

These two differences have huge implications for commercial enterprises. If Tomcat were licensed

under the GPL, any product that contained Tomcat would also have to be free software.

Furthermore, while the Apache License permits an organization to make modifications to Tomcat and

sell it under a different name as a closed source product, the GPL would not allow any such act to

occur; the new derived product would also have to be released as free software.

LGPL

The LGPL is similar to the GPL, with one major difference: non-free software may contain LGPL-licensed

products. The LGPL license is intended primarily for software libraries that are themselves free software

but whose authors want them to be available for use by companies who produce non-free software.

If Tomcat were licensed under the LGPL, it could be embedded in non-free software, but Tomcat could

not itself be modified and released as a non-free software product.

For more information on the GPL and LGPL licenses, see http://www.gnu.org/.

Other Licenses

Understanding and comparing open source licenses can be a rather complex task. The explanations

above are an attempt to simplify the issues. For more detailed information on these and other licenses,

there are two specific resources that can help you:

❑ The Open Source Initiative (OSI) maintains a database of open source licenses. Visit them at

http://www.opensource.org/.

❑ The GNU Project, mentioned above, has an extensive comparison of open source licenses

with the GPL license. See it at http://www.gnu.org/licenses/license-list.html.