Customers that use policies written for the OPA GK admission controller plugin (mutating webhook available) or the Kyverno plugin want to use their existing admission controller policies as written with ACS without having to manually rewrite those policies. 

Customers can use OPA GK or Kyverno with OpenShift today by deploying the community solutions or purchasing ACM. ACM provides and supports an OPA GK operator. 

Supporting these two additional ways of implementing deploy-time policies will enable faster customer adoption of ACS. 

Customer Reference: https://docs.google.com/document/d/1-Vi2jMqkNts02PN6CP_dgPt9SGfO_2Rou1K8WAM4re4/edit