Yes, that's right. On Linux, you already have readline installed. But neither Macs nor IPython can ship with readline itself, because of the GPL, so by default

Yes, that's right. On Linux, you already have readline installed. But neither Macs nor IPython can ship with readline itself, because of the GPL, so by default you get the inferior libedit. The Qt console doesn't require readline, but it does require Qt (and zeromq, and pygments).