After reading some Hacker News comments (ignoring 90% of them because they talk about Docker) I found this little gem from Brandon:
It isn't tied to systemd. The stage1 that is in the current prototype uses systemd to monitor and fork processes but we would love to see other stage1's that configure other process runners. For example configure and run a qemu-kvm filesystem as the container.
Also, even though it is using systemd to monitor and fork processes a design goal is to run on all Linux's that have a modern Kernel.