Software is only a piece of the puzzle

While MySQL is indeed open-source - licensed under the GPL - MySQL AB, the company in control of the project, sells services and support relating to their flagship product. Furthermore, the software is dual-licensed (as are many projects, such as the JavaScript library, jQuery), allowing the company to sell the product to clients that may not want the provisions of the GPL to be imposed upon their usage of the software.

With the traditional model of software, customers and clients pay for the software or a license to use it. In these newer models, almost all based around open-source, it is the value-added service and support that are at the heart of the business model. Note that MySQL AB is not the only company to do this; Red Hat has been around for years and they are certainly profitable. With the success of open-source software, I have to believe that this, at least in part, is the future of software development.

A great learning tool

Open-source software also highlights another point - the value it brings by easing learning. I remember when I was back in high school and starting to get into PHP and other web technologies. Naturally, with PHP came MySQL (back then at version 3.23), and it was the availability of this quality, open-source and easy-to-setup DBMS that prompted me to learn SQL. In my first real software project, creating the Cool Case Gallery for Virtual-Hideout, I used both of these languages, which have since become valuable assets for me. Kudos to MySQL and the open-source community for providing such great tools.