The focus for 1.0 is to offer the APIs necessary to customize Docker in every way you need - including custom sandboxing backends (like for example BSD Jails).

The focus for 1.0 is to offer the APIs necessary to customize Docker in every way you need - including custom sandboxing backends (like for example BSD Jails). There is now an execution driver API (which was indeed planned for 1.0), and now it's a matter of the community contributing and maintaining a BSD jails driver that works :) There are several efforts underway, but we (the core developers) can't contribute and maintain every driver possible, it would be too much work. If you're interested in participating come say hi on #docker-dev on Freenode, we can help you get started :)