Mesos is an Apache project. (DC/OS is not.) Apache projects are required to be vendor-neutral. That's part of the covenant under which contributors participate.

The Apache governance model provides opportunities for competing vendors, so besides Mesosphere, the market is open for other players to provide Mesos support.

Components aren't open source. Still waiting for the new hdfs package to be released see https://github.com/mesosphere/hdfs-deprecated/blob/master/RE...