Here’s how I did it:
Part 1: MIDI (the most difficult part)
1) I installed VLinn on my Mac via WineBottler, as described on Aly James Lab's website: http://www.alyjameslab.com/macosxsupport.html
2) In the Audio MIDI settings of my Mac, I created a MIDI port with the IAC Driver in the MIDI window.
3) In Logic, I set an external MIDI track’s output to the new MIDI port. (IMPORTANT: in the Environment window, it’s important you set the MIDI Physical input sources in the Click and Ports tab to only one device and not the sum, which is default! Otherwise, you will get MIDI feedback if the external MIDI track is record enabled!)
4) In VLinn MIDI settings, set the MIDI input to the same new MIDI port. It might be possible to use other MIDI inputs and outputs and have it still work, but I went on the safe side and used no others. Still, make sure “Pass Through to Output” is Unchecked.
Part 2: Audio
1) Download and install Soundflower.
2) Configure the VLinn’s audio output to Soundflower 64ch. This will definitely be necessary if you wish to use the multiple outputs feature of it.
3) Create an audio track in Logic, making sure the input channels are set to the output channels of Soundflower that you used for VLinn.
And voila! It’s not as convenient as having a single external instrument track, but it still works!