To compile you will need CCS's PCM compiler. The code is compiled and has been tested with PCM version 2.717 which is a pretty old version of the compiler. You will need to make some changes to have it compile with a recent version of PCM.
There are two hex files available. wx-s.dlog.hex is the data logging firmware and wx-s.aprs.hex is the APRS firmware. These can be programmed directly into a PIC16F628A. For the APRS firmware you will need to edit the EEPROM to your APRS location before burning your chip. Or you can change the wx-s.c source and recompile.