Der Mogwai ER Designer ist ein ER Modellierungstool wie z.b. ERWin. Es ist Open Source und wird bei sourceforge.net gehostet. Das sagt die Webseite:

The Mogwai ERDesigner is a entity relation modeling tool such as ERWin and co. The only difference is that it is Open Source and does not cost anything. It was designed to make database modeling as easy as it can be and to support the developer in the whole development process, from database design to schema and code generation. This tool was also designed to support a flexible plug in architecture, to extend the system simply by installing a new plug in. This way, everybody can implement new features and tools to make ERDesigner fit the requirements.

ERDesigner NG is based on Java and can be run on Windows and Unix systems
has a powerfull WYSIWYG for physical database design
handles tables, relations, indexes and comments
supports subject areas
supports MySQL, Oracle, Microsoft SQLServer and Postgres
creates the SQL DDL statements for schema creation
has an integrated schema version control system
can generate schema migration scripts for every change
stores the database definition as XML files for further processing
can export the database schema as GIF, BMP, JPEG or SVG files has an integrated reverse engineering module for existing schemas it is based on GPL license support is available by authors and newsgroups