Microsoft's "acceptance of open-source" only stretches as far as it helps them survive, in an economy where "why would I buy your product when there's this open-source thing" is a question that gets asked more and more frequently. You know, the "embrace" and "extend" phases of "embrace, extend, extinguish".

This is really obvious from the parts that they choose not to open-source, such as https://github.com/MicrosoftDocs/intellicode/issues/201