Earlier quoted context omitted.
even chunks of Azure are open source. https://github.com/Azure
Azure used to bill themselves as the "open cloud". That's kinda gone from their marketing, but they are WAY more open than AWS.
OVH, who owns the largest datacenter in North America uses OpenStack, they're actually one of the largest contributors. Red Hat & IBM both seem to be really pushing private deployments as of late for their larger clients that already own large DCs.