Are you referring to my posts about Logic 5&6 OMS and Sum input only? That's a real mystery. But on the subject of the Keyspan: You have to use OMS or Freemidi with the Keyspan. There are OSX drivers, but not for MIDI. The first two ports can emulate the printer and modem , in that order. I know the 4 ports will show in FreeMIDI setup, however I distinctly recall finding that only two are functional. On  one of the MDDs I run a Studio 5 and Studio 4, and it is GREAT. I don't run audio in Logic, only the MIDI sequencer. Sounddiver runs alongside, as does Unisyn when necessary, using OMS. The MDD model is a very smooth ride. I should add that I have three networked via Gigabit ethernet  switch, all while OMS is active. Now if you're so inclined, you can have a server connected running Tiger, then transfers for backups to it are very quick as opposed to those from OS9 to OS9 which are only 1.5 MBsec. Most often I run just the main MDD though. Simple is better.

using the term "ports" is vague. im assuming u mean the actual "serial ports" on the card.. and not "midi ports" provided by a connected interface.

2 serial ports is all that will ever be able to work with oms as oms was written for real macs that only had 2 serial ports so its only written to handle 2 serial ports..  other names for these 'ports' include: rs-422, rs-232, geoport