A bit uglier but if you need to support quite a few databases maybe Razor is another good alternative. I've used it for years. It is not open source though.
Razor is actually quite impressive - I've made it the default SQL client tool for the team.
It works on Windows, OS X and Linux, connects to almost any RDBMS in existence, easily customizable and has tabbed results interface in addition to many other features.
All for $60-70. Easily worth the money, you can get a full trial for 30 days to see if it works for you.
"Induction supports PostgreSQL, MySQL, SQLite, Redis, and MongoDB out-of-the-box"