This macbook doesn't have a hard ethernet port either. Now when I try to install bcmwl-kernel-source from the command line, it tried to upgrade lib6c (and a few other packages) that aren't on the live stick. This seemed to work and I was able to add the 'cd' to apt with apt-cdrom.
I figured I would outsmart it and I mounted the USB stick on /media/cdrom. I think this is because KDE mounts the USB stick on /media/user/VOLUMENAME I got a similar message when doing apt-get install bcmwl-kernel-source from the CLI. I got an error about not being able to find the Release file on deb cdrom. I open Driver Manager and choose the broadcom driver, but it fails to install it from the USB stick. When I install to the hard drive and reboot, I don't have Wifi (as expected). After I boot into the live session I can start Driver Manager and easily install the Broadcom driver to get Wifi working.
