Earlier quoted context omitted.
After all there aren't many high quality opensource RDBMS GUIs available. The only one I know is pgAdmin and even pgAdmin has some serious bugs. (GUI freezes easily when you have many windows open and/or do large queries; import/export barely work) The only code I would trust is the code I generate myself... ;)
DbVisualizer ( http://www.dbvis.com/ ) is an excellent cross-platform, multi-product GUI tool. Doesn't have many design tools (well not any really, but neither does PgAdmin). Java-based and not free, which gives freeloaders and snobs something to complain about. No relationship, just someone who has been happy to be a customer for many years.
Someone posted a link to a modelling tool.