What the users are free to do, however, is use an operating system/stack that they CAN evaluate the source of.
If linux or any other open source alternative was a better actual product, it would find its way to the top of the market. In fact, it already has, on the server... by far. But linux wasn't made to be easy to use, to be quick and easy to install, to install other software onto, etc... and that has kept it back, and it kept it back long enough for microsoft to establish a de-facto standard on the home desktop market...
The closed or open source status of a product has no bearing over its superiority at all. Again, in the world of geeks, it may, but in the world at large, it doesn't, and really, it shouldn't.