I know the PiCapture HD1 was made to work with the Raspberry Pi. I guess it is connected via the GPI/O pins on the board. What would have to be done to use it on another single-board computer, that also has GPI/O pins?
In my case that would be a Pine A64.
Would I have to re-write the driver by myself?
The PiCapture boards work by emulating the Raspberry Pi camera, and the primary interface is the MIPI CSI-2 ribbon connector. The GPIO connector is only used for power and the control interfaces (serial or I2C).
The Pine A64 camera interface is not compatible with the Raspberry Pi camera, and so you would not be able to use PiCapture with that board.