Bitstamp support has been officially added.

We will indeed be adding Bitstamp. In fact it's scheduled to be included today or tomorrow. All added exchanges can be enabled or disabled at the user level so ultimately it is up to the user as which exchanges they would like to perform arbitrage opportunities on.

The core of the platform is developed in Node.js although individual clients will also be created in various languages. Once the API becomes public client access can be developed in any desired language.