i´ve always used a patched 304 to reauthorize 305.
but i also own a legit copy; sounddiver was one of classic cases of "buy it but install the crack", because noone wants to fiddle with various optical media during creative work.
there is another reason why it might be so hard to get a license second hand: sounddiver is somehow essential and unique, and it is almost impossile to migrate to a newer app. so many people just keep their copy to use it with their old grear.
it is a matter of taste - and also depends on the gear you need to control - but in my opinion cubase, unisyn or the later midiquest (which is a mess of a computer code assemblement and contains even more bugs than sounddiver did) could never compete.
an OSX user in the need of control over post-2003 hardware might eventually want to get into
http://ctrlr.org/ and build his own stuff today (or in my case, max/msp or supercollider).
running an old OS9 notebook only for sounddiver side by side with another computer stops beeing fun when you need that on a daily basis, for example in conjuntion with DAW projects or on stage.
