Reuse a microphone (formerly) wired to the digital "General Purpose Input/Output" of a Realtek sound card?
If the signal to the microphone really is digital, then there has to be an IC on the camera module that does the conversion. You need to find that IC and see if there is a datasheet for it.
1) Find all the chips labeled with U designators.
2) Find the datasheet for the chip see if its has anything to do with microphones
3) Figure out how to interface with the microphone IC

The memory chip is probably to identify the camera board.

I see a U3 and U7 on the back of the board, they are located under the EMI shield. I'd place bets that U7 is for the camera and U3 is for the mic.