The company isn’t offloading all responsibility. It’s promising to contribute new features to the project, including a developer kit package for the Unity game engine. This will mainly help developers adapt to new phone displays and other changes without waiting for Google.
The open source effort might be a relief to some. Cardboard is widely considered one of the most affordable ways to experiment with VR, and Google said it still has “consistent” uses in entertainment and schools. If Google simply halted work on Cardboard, the future of those efforts would have been uncertain at best — open code gives creators at least some options for keeping their projects alive.