commercial counterparts. This document addresses these issues for today's most popular Web
application Open Source products by taking a close look at what is available, and giving the
reader a starting point by providing a technical introduction and many selected references.
2 Current Open Source Standards A Brief Overview
2.1 What is Open Source?
Before diving into the different Open Source technologies, it is helpful to look at where Open
Source came from, and the motivation behind it.
When developing applications, it is important to understand both the rights and obligations that
come with using Open Source software, since this can affect the newly developed product itself.
While Open Source implies that the source code is available and modifiable, the use of the
program is free, and copies may be made, it often also means that the same rules have to apply
to the program that utilizes Open Source, depending on the type of license that the Open
Source software is provided under.
It is also worth mentioning that free software, freeware, public domain, and Open Source don't
mean the same thing, although all of these products can be obtained free of charge.
Recommend references are given below for readers interested in a more detailed discussion of
The term Free Software is based on the idea of making software accessible to anyone for free,
including the right for everyone to make improvements to it. This implies that the source code is
provided with the software product. To protect the rights of the authors, a formal approach
through licenses has been introduced through Richard Stallman, a former member of the MIT
Artificial Intelligence Lab, with the founding of the Free Software Foundation (FSF) in 1984.
Stallman's goal was to develop a UNIX compatible operating system called GNU (= GNU's not
UNIX) which should give users a portable, no cost alternative to the various UNIX systems that
were specific to each hardware vendor. He planned to achieve this by gradually replacing the
proprietary versions of the UNIX system software components with his and other voluntary