I'm designing a board around a PIC18F6680, and the datasheets mention that programming can be done with only 2 pins. (PGC and PGD, although MCLR and GND are needed too). In a bunch of posts on here, people say that PGM needs to be grounded with a Resistor.

does it really need to be grounded, or can i use it as an I/O?