As I and several other members have stated the Oshonsoft Simulator IDE is BASIC not 'C'. What the simulator does when a hex file is generated a 'asm' file is generatered then the simulator uses that 'asm' file to simulate the code. In order to use Mplab to program a hex file generated by OSI you simply load the 'asm' generated file in mplab and ensure the config fuses and the include files are present in the 'asm' code.
The Oshonsoft compiler has come along in leaps and bounds in recent months and in my opinion it is one of the best low cost- feature packed pic Basic IDE's around today. How many other IDE's will let you make external modules to allow you to fully simulate your code?
Cheers Bryan