Facebook has released the open source version of their platform called fbOpen. You can get a copy of it here. I wrote about this earlier this month but it has now officially launched. Facebook posted the following release notes regarding the launch:

This release includes the API infrastructure, the FQL parser, the FBML parser, and FBJS, as well as implementations of many common methods and tags. We’ve included samples and some dummy data to help you get started fast.

Facebook Open Platform also has extensibility points built in so you can add your own functionality, such as your own FBML tags, API methods, etc.

Additionally the only restrictions on the platform license is that “you include attribution to Facebook on any modifications” and that “network deployment, or making modifications available over the network, counts as distribution, which makes the license appropriate for Web services.” It will be interesting to see if this is implemented by other social networks to launch their own platforms.

This is also clearly a jab at Google which is trying to make the OpenSocial standard the default for the social web.