Author here. For more discussion on init handling you may find my article on pid namespaces[1] enlightening. In terms of differences from runc, there aren't many. The goals for railcar are threefold:

1: provide an alternative implementation of the oci-runtime so that the spec doesn't become too locked to a single implementation.

2: provide an implementation in a single language without some of the "baggage" of the existing implentations so that it is easy and fun to hack on.

3: experiment with new ideas to inform the future of the oci-runtime spec.

[1] https://hackernoon.com/the-curious-case-of-pid-namespaces-1c...