Java Reference
In-Depth Information
accorded to third-party libraries licensees. In this case, developers have to include in their dis-
tribution the provided JAR files without any modifications.
Consult vendor's redistribution policy documents or contact them directly for any inquiry.
Open Source Libraries
Given the possible confusion that could arise for open source contracts, we discuss here this
increasingly common case. The kind of use that can be made of such libraries is basically of
two types: including the libraries in your applications and (wherever the sources are available)
eventually modifying the sources.
For a handy list of all the major open source licenses, visit the following URL:
http://www.opensource.org/licenses/
.
There are a large variety of open source licenses. It may be of some help to briefly mention the
main types, as regards software deployment. All the following license types permit to redistrib-
ute software at no cost and provide to developers the source codes as well.
•Royalty-free libraries that can be used freely, but cannot be modified by user program-
mers, even if sources are publicly available.
•Licenses that allow for source modifications, such as the BSD licensing model. BSD-
style licenses allow for open source software to be combined with proprietary software
and be licensed with no restrictions (that is, also as proprietary software itself). It
requires a citation of Licensing Authority in any derivative use. The Apache licensing
model permits public check-ins to the core libraries as well.
•Finally, licenses that allow for sources modifications, public check-in of code, and
impose the constraint that all derivatives must be free. The General Public License (GPL)
used for example for GNU or Linux licensing. Under the GPL, you can distribute the
original work or its derivatives to whomever you like, as long as you make readily avail-
able the source to the original work, the modifications you obtained, and any modifica-
tions you made. Any licenses you give must also follow the GPL restrictions.
Be aware of the type of open-source license with which your executables come shipped.
Depending on the particular license, often you may only distribute the software and the modifi-
cations in a compiled form as long as some added value is provided (for example, IBM's
XML4J package commercial license).
A brief mention about the so-called ”Viral Clause” used among the others by the GPL license.
This clause requires that software incorporating fragments of GPL-licensed code be licensed
(in its entirety) under the GPL. A compromise version, the Library GPL (LGPL), permits other
software to use (and redistribute) a LGPL-licensed library without itself being under the GPL.
