For Mac users, here are the steps (DO THIS AT YOUR OWN RISK - I TAKE NO RESPONSIBILITY):
1. Download HexEdit (free) and create a new file.
2. Copy Antoine's 1 line of code listed above (he gives an example for changing to channel 8 or 12)
3. Paste that 1 line of code into HexEdit.
4. Make any necessary change to set it for the correct channel you want to use. Turns out that I really wanted to use channel 16, so I changed the 'c' to 'F'.
5. Save the file. I called mine 'sysex.syx' (without the single quotes, of course).
6. Download Sysex Librarian (also free).
7. Make the sure that the AFE keyboard is turned on and connected via USB.
8. Sysex Librarian will list all of the MIDI devices connected to your Mac. Select the AFE.
9. Click on 'Add' then point it to the file you created in step 5.
10. Click the Play button.
That's it! It really is pretty easy, maybe 15 minutes tops. Check to make sure it worked correctly by setting the AF software to use only the specific channel you switched to, then play a note on the keyboard. You should be getting audio. Now set it to receive on channel 1 and hit a note on the keyboard; you shouldn't hear anything.
At this point the keyboard is transmitting on the new channel, so set the software to receive on 'all' or on the new channel. Mine is now set on 16 and does not interfere with any of my other gear - at least not that I know of!