MySQL Community edition is free to use, whether you are a home user or a billion-dollar corporation. You can store your data in it, serve Web pages from it and build reports that rely on it, all without paying a dime. However, if you plan to sell a product that requires MySQL to function, or a product with built-in functionality to use MySQL, you must buy a commercial license. Of course, if you want official support, you'll need to pay for that too.
This was first published in December 2006