AFAIK they want to spin out the reusable components off Docker (more than already done in libcontainer), including the code responsible for storage volumes, networking, etc.

Basically, make all the building blocks of Docker available as a library, with some framework to use to connect them.

Probably the Docker project would become the blessed customer of this new framework.

I can't really see rkt, snap, OpenShift adopting this technology, though.

Edit: as many of the things they want this framework to do belong to orchestration (if there are several containers involved--they often are), this might also look like a pinch at Kubernetes.

This is github.com/docker/docker with a note added on top of the README.

For now you have to watch the DockerCon keynote to understand; it's intended as a "common assembly line for container systems".