Damn. I was hoping this would be a Postgres client, not a bundled server. pgAdmin works, but it's a pain. Sequel Pro is orders of magnitude better.
"Induction supports PostgreSQL, MySQL, SQLite, Redis, and MongoDB out-of-the-box"
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.
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.
I use it a lot, and have nothing but praise for it.
I'm still holding out for Postgres and Sqlite support in Sequel Pro since that tool has a great UI and tons of nifty features.