How much has google really open sourced? Think about it. Search engine? Gmail? Ad engine? Maps? Drive? Youtube? Nothing!

Google has a lot of development tools open sourced, almost no products. Android is one for a change, but with Google Play Services, most of what you really use is closed source.

Microsoft has tons of source code out there too, but no windows, no office... For VS I think it's a matter of time. But the point is: should they? What is the advantage?

Apple seems to be doing fine with developers, and how much of it is open source? In fact people like to pay more for apple hardware in order to talk about how free things should be.

I'd go further and hypothesize that it's only a matter of time before Windows is open-sourced. The main obstacle to that has historically been a perceived need to sell each and every copy of Windows at a massive markup, but the current trends indicate - to me at least - that Microsoft is slowly warming up to the idea of being to Windows as Red Hat is to its variety of GNU/Linux or Google is to Android: use it as a vehicle to deliver a product (Red Hat's support contracts, Google's ad delivery and such) rather than the product in and of itself.

Here, Microsoft will still make plenty of money; businesses would still want support contracts, after all, so Windows could be monetized like RHEL with Microsoft selling support contracts to medium and large enterprises. Selling Windows itself has been an obsolete business model for quite some time, and I have a good feeling that Microsoft is now starting to realize that.