The Commercial License, which allows you to provide commercial software licenses to your customers or distribute MySQL-based applications. This is for organizations that do not want to release the source code for their applications as open source / free software; in other words they do not want to comply with the GNU General Public License (GPL). (emphasis mine)

For those developing open source applications, the Open Source License allows you to offer your software under an open source / free software license to all who wish to use, modify, and distribute it freely. The Open Source License allows you to use the software at no charge under the condition that if you use MySQL in an application you redistribute, the complete source code for your application must be available and freely redistributable under reasonable conditions. MySQL AB bases its interpretation of the GPL on the Free Software Foundation's Frequently Asked Questions.

Looks like we're both slightly in error. (I based my conclusions on the class I took a year ago.)