Re: So does this mean..
Of course not
You can still install anything from anywhere
Anything that runs under X11 will continue to run for example. Though you will have to install X11 separately You forget that a great deal of gear that apple uses as it's default install is open source.
Mach Kernel, Darwin, CUPS, Webkit etc.
Here's 200 other open source projects that apple supports
and here's a dev link