Software
The board support package now sits on a long-term supported kernel series. The camera, display and networking drivers on the AM67A were adapted to the new kernel interfaces as part of the move, and the device tree layer was simplified.
For developers upgrading an existing project, the configuration keys that changed and the patches that were dropped are listed in the release notes in the repository. The source is still distributed under the same open source licences as the SDK.
If your own board behaves differently after the upgrade, the BSP thread on the forum is the place to say so.