I can see Microsoft's dilemma here. Clearly all the goodwill etc. would be great for Microsoft if they open sourced MCM, however, it would be providing comprehensive training materials for versions of SQL Server that they would rather we all would be upgrading from.

I can see the benefits to the community and thus to Microsoft but as what cost?

Part of me doesn't care about Microsoft making money. Part of me does. I have made a living as an [make it up - in your own mind you can either think well of me or not] mainly within the Microsoft stack so my continuing success depends on Microsoft's continuing success. Yes, I could easily transfer my skills to different technologies but the definition of "easily" does not include "without effort" 😉

Having said that, I believe that open sourcing the material would be better in the short/medium term for DBAs et al AND would be good for Microsoft in the long term.