I spend significant time helping the effort (Brandon Philips, CoreOS).

But, today there just isn't anything to implement in rkt. The primary focus of OCI has been a rootfs on-disk and a json file that contains details of cgroups, namespaces, etc. This is fine work to be doing but it doesn't tackle the more difficult and useful work of creating inter-op for developers up the stack who don't care about the internals of containers.

Here is a high-level post on the state of the world: https://coreos.com/blog/making-sense-of-standards/

Here is a video that I gave that summarizes some of my thoughts: http://containersummit.io/events/sf-2015/videos/container-ec...

A more detailed discussion on the OCI mailing list from earlier this year: https://groups.google.com/a/opencontainers.org/d/msg/dev/uo1...

tl;dr Container formats are important to get right. But, today the OCI effort is largely irrelevant for people packaging and shipping their code in a application containers.

edit:

Also when OCI finally makes it to a stable release we will likely add tooling to help import into rkt: https://github.com/coreos/rkt/pull/1509