The Open Source Advantage
I use open source software to develop and maintain all of my clients' websites. Open source software is created and updated by communities of computer programmers, and the resultant "source code" (the underlying instructions that make up the program) is made freely available. This is different from proprietary software products such as those of Microsoft, where access to the code is a big secret.
Open source offers maximum flexibility because the underlying code can always be changed specifically for each project if needed. Open source software is also usually distributed freely, which translates into significant cost savings for my clients.
Why would anyone develop software and give it away?
Many people are shocked when they hear that major software programs are noncommercial and legally free to adopt and use for one's own purposes. There are two major reasons why excellent software is freely available. First, major companies that sell hardware, like IBM, help pay for and develop open source software to bundle with their products to add value. By opening the code to the community, the companies are able to benefit from the contributions of other programmers, and as others adopt their code, they benefit from increasing standardization.
Second, there are many people who believe that programs' source code should be freely available, and put this belief into practice by releasing the source code to the public. Think of it as a kind of intellectual charity.
What open source programs do you use?
My clients' websites are hosted on industry standard Apache web servers. Database-driven stores and community sites use a combination of PHP scripting and MySQL databases. Content management systems I employ include Drupal and Joomla.
For development, I use Ubuntu, a distribution of Linux, alongside tens of applications to create each website.
Legal Implications of Open Source Software
An excellent guide is available from the Software Freedom Law Center.
More Information
For more information on open source software, I recommend reading the article What is Open Source?. Other useful publications include the Open Source definition (from the Open Source Initiative) and the GNU General Public License version 2.