Muxed means as many as 8 functions can be connected to a pin based on the register setting in the chip. It is controlled by SW.
McBSP is most commonly used for audio CODECS.
I suggest you get the TRM for the DM3730 from TI and read through it. Try to convince yourself that it is interesting and has a great story line!
Hmmm this audio codec, is it the same one that the on board audio in and audio out jacks use? Or are the additional ones.
In other words if I chose to use the above mentioned pins on the expansion port as gpio's, will that kill the audio?
Ideally I want a few gpio's connected to stuff while still maintaining a fully functional Linux os.