Holy refuctoring! Sorry for the change, but some libraries were having naming conflicts. You can define SPINE_SHORT_NAMES before including spine-c headers if you want to use structs and functions without the "sp" prefix, as it was before.
This has some API breakage, sorry. The new AnimationState now handles multiple "tracks", which makes it easier to apply and queue multiple animations at the same time, no longer do we need multiple AnimationStates.
Changed from New BSD to a custom license. The new license requires a Spine license to use the code. If you have a valid Spine license, you can do whatever you like with the code. This should not be a problem for anyone using the runtimes with Spine, nothing changes. If using the runtimes without a Spine license, you now need a Spine license. This is because the runtimes were created explicitly to be used with Spine.
There are no longer separate animation files, they are now inside the skeleton file. This means there is just one file to manage, which is cleaner. Now that animations are stored in SkeletonData, they can be looked up by name which leads to cleaner runtime APIs.
cocos2d and cocos2d-x runtimes got a cleaner ObjC/C++ API.