This is true to a point. But there is the risk of building open source applications that are tied into closed source OS stuff. Like you could build some great t

This is true to a point. But there is the risk of building open source applications that are tied into closed source OS stuff. Like you could build some great thing that is completely dependent on Dirext X for instance. Sure you have ht code but it is functionally useless without that missing piece. There is also the issue of sheer code size/complexity that means even if you have the code, do you have enough people to verify it or is it a case of just waiting until it breaks/gets exploited? That second point is a larger issue of open source nowadays, not just Microsoft.