MySQL's Workbench licensing decision really isn't much of a question of proprietary versus open source. It's about speed of development.

Although the free cost of MySQL Workbench is very attractive, performance is less than stellar when strained. Many users have also reported MySQL Workbench hangs or fails to respond.

If you plan to do database development with Java and MySQL, the first thing you’ll need to do is configure a database schema. Technically speaking, the first thing to do before you configure a schema ...

The MySQL Workbench GUI is cross-platform, open source, and incredibly easy to use.