From what I understood:
If you use MySQL "as is" just for the testing purposes - you are free to use it.
If you modify the MySQL
- you are still free to use it BUT you have to make the modifications you made public
(GPL is "transfering")
If you redistribute MySQL or work derivated from MySQL in any way, then this says it all:
Q3: As a commercial OEM, ISV or VAR, when should I purchase a commercial license for MySQL software?
A: OEMs, ISVs and VARs that want the benefits of embedding commercial binaries of MySQL software in their commercial applications but do not want to be subject to the GPL and do not want to release the source code for their proprietary applications should purchase a commercial license from Oracle. Purchasing a commercial license means that the GPL does not apply, and a commercial license includes the assurances that distributors typically find in commercial distribution agreements.
