We have added a new feature to list ancestor codes and child branches with a "fork tree". When the code has forked version or itself is a child branch of an existing code, then "tree" link will be displayed on the info, so that you can track down the fork history.
Along with creating this feature, we have started rolling out jsdo.it API.
jsdo.it API's documentation
The domain is "api.jsdo.it", but we have set the Access-Control-Allow-Origin header to make access possible via ajax. Try building your own original fork tree.