Open-source and free software communites for the most part are still going to be distrustful of Microsoft (and their spin-offs) as long as the company continues to extract patent licensing fees from companies that make use of Linux.
The foundation of a new legal entity for open source is not any sort of magnanimous move on the part of Microsoft. It is a standard maneuver in companies wishing to take advantage of open source projects: create a separate company just to avoid GPL poisoning your products.
And this is perfectly fine. For instance, Qualcomm set up Code Aurora specifically so that they could keep their propriety and open source offerings separate.
The shifty thing here is that Microsoft is trying to paint this as some sort of altruism, as thought Microsoft is doing the open source world a favor by setting up a legal formality.
