The screenshot you show comes from [WWW SQL Designer](https://code.google.com/p/wwwsqldesigner/):

- free and open source (New BSD License)
- [online demo](http://ondras.zarovi.cz/sql/demo/)
- retrieve (import) schema from existing database.
- cross-platform (web application)

Description from the website:

> This tool allows you to draw and create database schemas (E-R
> diagrams) directly in browser, without the need for any external
> programs (flash). You only need JavaScript enabled. The Designer works
> perfectly in Mozillas (Firefox, Seamonkey), Internet Explorers (6, 7,
> 8), Safari and Operas. Konqueror works, but the experience is limited.
> 
> Many database features are supported, such as keys, foreign key
> constraints, comments and indexes. You can either save your design
> (for further loading & modifications), print it or export as SQL
> script. It is possible to retrieve (import) schema from existing
> database.