To determine whether or not you need a MySQL license when selling your application, you should ask whether the proper functioning of your application is contingent on the use of MySQL and whether you include MySQL with your product. There are several cases to consider:@:
mysqld server. For example, if you've designed your
application around MySQL, then you've really made a commercial
product that requires the engine, so you need a license.
If your application does not require MySQL, you need not obtain a
license. For example, if MySQL just added some new optional
features to your product (such as adding logging to a database if
MySQL is used rather than logging to a text file), it should fall
within normal use, and a license would not be required.
In other words, you need a license if you sell a product designed
specifically for use with MySQL or that requires the MySQL
server to function at all. This is true whether or not you provide
MySQL for your client as part of your product distribution.
It also depends on what you're doing for the client. Do you plan to provide
your client with detailed instructions on installing MySQL with your
software? Then your product may be contingent on the use of MySQL;
if so, you need to buy a license. If you are simply tying into a database
that you expect already to have been installed by the time your software is
purchased, then you probably don't need a license.
mysqld server,
because in this case you are selling a system that includes MySQL.
This is true whether the use of MySQL with your product
is required or optional.