Matchstick isn't a Mozilla project, is it? It happens to be built on Firefox OS code, but anyone can use that code, and Matchstick is made by a third party. Mozilla can't prevent someone from building a Firefox OS product and adding Microsoft DRM to it.

So I think the "they" in your statement there might be confusing, as it seems to imply Mozilla is doing something here.

(btw, I hadn't heard about this latest development with matchstick regarding Microsoft DRM, link?)