The PICkit 1 firmware and host software source code can be
download from Microchip website. By the way, they have host
software code for the Mac OS X as well.

http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1960
Unsupported Source Code

Here is the revision history for the firmware.

;***************************************************************************
***
;Filename:	PICkit.asm
;Author:	Reston Condit
;Date:		19 September 2003  	
;Version:	2.00
;Description:  	
;  This firmware is written for the PICkit(TM) 1 FLASH Starter Kit. 
;
;***************************************************************************
***
;Revision History:
;  9/19/03	RAC	Added functionality:
;				Write four words at a time
;				Transfer data to flash device
;				Get data from flash device
;				Abort transfers
;				Enternally timed writes
;			Reorganized usb files and PICkit 1 specific code on
;			 specific pages.  All PICkit 1 code is on page 1 of
the
;			 program memory.  All USB related functions are on
page
;			 4 (with the exception of ServiceUSB and several
user 
;			 called functions - see top of usb_ch9.asm.)  Have a

;			 look at the pickit.map file for details on memory 
;			 organization.  Most of the "pagesel" statements
were
;			 taken out of all the file in order to save space
and
;			 clean up the code			
;***************************************************************************
***

http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1960
Unsupported Source Code

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