The MySQL software is released under the GNU General Public License (GPL), which is probably the best known Open Source license. The formal terms of the GPL license can be found at http://www.fsf.org/licenses/. See also http://www.fsf.org/licenses/gpl-faq.html and http://www.gnu.org/philosophy/enforcing-gpl.html.
Since the MySQL software is released under the GPL, it may often be used for free, but for certain uses you may want or need to buy commercial licenses from MySQL AB at https://order.mysql.com/. See http://www.mysql.com/products/licensing.html for more information.
Older versions of MySQL (3.22 and earlier) are subject to a stricter license (http://www.mysql.com/products/mypl.html). See the documentation of the specific version for information.
Please note that the use of the MySQL software under commercial license, GPL, or the old MySQL license does not automatically give you the right to use MySQL AB trademarks. See MySQL AB Logos and Trademarks.
The GPL license is contagious in the sense that when a program is linked to a GPL program all the source code for all the parts of the resulting product must also be released under the GPL. If you do not follow this GPL requirement, you break the license terms and forfeit your right to use the GPL program altogether. You also risk damages.
You need a commercial license:
When you link a program with any GPL code from the MySQL software and don't want the resulting product to be licensed under GPL, perhaps because you want to build a commercial product or keep the added non-GPL code closed source for other reasons. When purchasing commercial licenses, you are not using the MySQL software under GPL even though it's the same code.
When you distribute a non-GPL application that only works with the MySQL software and ship it with the MySQL software. This type of solution is considered to be linking even if it's done over a network.
When you distribute copies of the MySQL software without providing the source code as required under the GPL license.
When you want to support the further development of the MySQL database even if you don't formally need a commercial license. Purchasing support directly from MySQL AB is another good way of contributing to the development of the MySQL software, with immediate advantages for you. See Support.
If you require a license, you will need one for each installation of the MySQL software. This covers any number of CPUs on a machine, and there is no artificial limit on the number of clients that connect to the server in any way.
For commercial licenses, please visit our website at http://www.mysql.com/products/licensing.html. For support contracts, see http://www.mysql.com/support/. If you have special needs or you have restricted access to the Internet, please contact our sales staff via email at <sales@mysql.com>.
You can use the MySQL software for free under the GPL if you adhere to the conditions of the GPL. For additional details, including answers to common questions about the GPL, see the generic FAQ from the Free Software Foundation at http://www.fsf.org/licenses/gpl-faq.html. Common uses of the GPL include:
When you distribute both your own application and the MySQL source code under the GPL with your product.
When you distribute the MySQL source code bundled with other programs that are not linked to or dependent on the MySQL system for their functionality even if you sell the distribution commercially. This is called mere aggregation in the GPL license.
When you are not distributing any part of the MySQL system, you can use it for free.
When you are an Internet Service Provider (ISP), offering web hosting with MySQL servers for your customers. We encourage people to use ISPs that have MySQL support, as this will give them the confidence that their ISP will, in fact, have the resources to solve any problems they may experience with the MySQL installation. Even if an ISP does not have a commercial license for MySQL Server, their customers should at least be given read access to the source of the MySQL installation so that the customers can verify that it is correctly patched.
When you use the MySQL database software in conjunction with a web server, you do not need a commercial license (so long as it is not a product you distribute). This is true even if you run a commercial web server that uses MySQL Server, because you are not distributing any part of the MySQL system. However, in this case we would like you to purchase MySQL support because the MySQL software is helping your enterprise.
If your use of MySQL database software does not require a commercial license, we encourage you to purchase support from MySQL AB anyway. This way you contribute toward MySQL development and also gain immediate advantages for yourself. See Support.
If you use the MySQL database software in a commercial context such that you profit by its use, we ask that you further the development of the MySQL software by purchasing some level of support. We feel that if the MySQL database helps your business, it is reasonable to ask that you help MySQL AB. (Otherwise, if you ask us support questions, you are not only using for free something into which we've put a lot a work, you're asking us to provide free support, too.)