Our software is 100% GPL (General Public License); if yours is 100% GPL compliant, then you have no obligation to pay us for the licenses. This is a great opportunity for the open source community and those of you who are developing open source software.
The formal terms of the GPL license can be found in the GNU General Public License section of the MySQL Reference Manual. Please note that the General Public License can be restrictive, so if it doesn't meet your needs, you are better served by our Commercial License.
Specifically:
MySQL is free use for those who are 100% GPL. If your application is licensed under GPL or compatible OSI license approved by MySQL AB, you are free to ship any GPL software of MySQL AB with your application ('application' means any type of software application, system, tool or utility). You do not need a separate signed agreement with MySQL AB, because the GPL license is sufficient. We do, however, recommend you contact us as there usually are good opportunities for partnership and co-marketing.
Under the Open Source License, you must release the complete source code for the application that is built on MySQL. You do not need to release the source code for components that are generally installed on the operating system on which your application runs, such as system header files or libraries.
Free use for those who never copy, modify or distribute. As long as you never distribute (internally or externally) the MySQL Software in any way, you are free to use it for powering your application, irrespective of whether your application is under GPL license or not.
You are allowed to modify MySQL Software source code any way you like as long as the distributed derivative work is licensed under the GPL as well.
You are allowed to copy MySQL binaries and source code, but when you do so, the copies will fall under the GPL license.
Optional GPL License Exception for PHP. As a special exception, MySQL AB gives permission to distribute derivative works that are formed with GPL-licensed MySQL software and with software licensed under version 3.0 of the PHP license. You must obey the GNU General Public License in all respects for all of the code used other than code licensed under version 3.0 of the PHP license.
FOSS Exception. We have created a license exception which enables Free and Open Source software ("FOSS") to be able to include the GPL-licensed MySQL client libraries despite the fact that not all open source licenses are compatible with the GPL.Read more about the exception.