All of this is being contributed under the governance of the Docker project. If you believe in the Apache 2 license, then this should in no way be bad for Open Source.
At a lower level, this is strengthening a proprietary platform, and might lower adoption of FOSS platforms.
At a higher level, co-opting an open source technology to deliver closed source software may indicate a strategic flaw in our approach to FOSS. On Microsoft's part this is clearly a continuation of 'embrace and extend'.
They'll use docker to provide the functionality and build hype until they can build their own version into the OS by default. Docker on Windows becomes obsolete, and everyone runs apps on Azure.
